I feel for you Stardust22 and my heart aches for you both. It is distressing to feel out of control when parenting a challenging child and it is all too often a very lonely business.
One of my children has presented this kind of challenging behaviour since before he turned one, and more than a decade and a half later he still is challenging to parent.
I was so very desperate by the time he started nursery, I felt I couldn't cope with him anymore. We explored all kinds of possible root causes for his aggression and out of control behaviour, ODD, ADD, ASD, deafness, obscure and common allergies, food sensitivities...
Being told at pre-school and school, that no, he's behaving beautifully for us, I don't recognise this child that you describe and nothing about him suggests he has any of those conditions was upsetting.
At some point I couldn't help but wonder if the problem wasn't him but us. As other pp have pointed out, children tend to
- model the behaviour of their parents
- engage in patterns of behaviour that work for them
- meet their parents' expectations, especially the bad ones
At age three and a half you had a child react to a stressful situation in a not uncommon involuntary compulsion to withhold his stool. This isn't misbehaviour or naughtiness or defiance or anything else that's about your relationship with him, it is a reaction to a situation where he feels out of control. It's not personal. I've encountered quite a number of children who did this, one of my own (a most agreeable child) did too.
It is incredibly hard for the child to stop the behaviour as once it becomes a habit this involves physiological processes they cannot fully control, despite their best efforts, and when they do have to go to the toilet it can be painful and the urge overwhelmingly powerful. It's a vicious cycle to be caught up in for both parents and children.
But what it is not is misbehaviour.
Later you describe a perfectly obedient child, who duly accompanied you to the car after playing in the park. A child who much to his misfortune then gave voice to his entirely age appropriate disappointment that something he enjoyed very much was over and he was very much powerless to avoid that happening.
And so he lost the privilege of after-school park visits permanently. You don't say how many years ago that was, but in any case for an age appropriate misbehaviour he deserved an age appropriate consequence that would help him learn to express his disappointment in an age appropriate manner. What he got was a vengeful punishment that is lasting to this very day. When will the punishment be over? What lesson is he learning now? How can he earn these park visits back?
I'm not simply being mean here, these are questions I had to confront myself. After that last parent-teacher conversation I did not immediately understand just what I was doing that had locked us into a never-ending and forever escalating power struggle with our son. But I did finally have to consider that the problem was us and not him. What's so difficult about that realisation is that we can't easily change someone else, especially not when you're locked into a struggle involved ingrained patterns of behaviour. But we can change how we react to others and then we can start to change these patterns. Which is what we did over a number of years.
Despite what many pp are suggesting in their sympathy for your struggle, there may well be a different reason why no professional has been willing to refer your son to date. Not every bad behaviour is caused by any number of conditions, even though that is always something to take into account.
Sometimes our parenting efforts do fall short. We pick up the wrong advice, we fall into bad habits, we think we follow common sense when sometimes it's neither common nor making sense.
For instance, I don't know who taught you that the most important thing about disciplining your children was to follow through on any threats you make. (That's what I get from your posts - once you make a threat, you have to follow through however inappropriate or ineffective they may be.)
Despite what most people seem to think "disciplining our children" does not actually refer to punishment. It is the long and arduous endeavour to equip our children with the ability to make good choices when we are not there to make these choices for them. When your threats are absent.
That's your longterm goal.
Not to put the fear of you in him, not to teach him a lesson he'll never forget, not to make him see that you will follow through on your threats.
It may involve punishments at times, but mostly it involves setting age appropriate boundaries, presenting clear, age appropriate consequences with an age appropriate duration, opportunities to make amends and most importantly avoiding punishments that are retaliative in nature. And yes, this is bloody hard work. So pick your battles - not every misbehaviour must be punished. And even if you do all that, you'll still make mistakes and have to adjust your system. Try to start every day with a blank slate for you and your son - reset to annoyance level zero and don't carry your anger, frustration and pain over into your parenting. It's really not productive.
I do agree with some posters that your child's behaviour should indeed set alarm bells ringing, but not for the reasons you worry about. He may well need therapy, or better still would be family therapy. His behaviour strongly suggests that he is struggling with feelings of worthlessness, that he is lashing out at a world that is hurting him. He's been branded the black sheep in the family, you prejudice every education professional against him by emphasising his terrible behaviour at home. He knows this. He's probably heard you tell others how bad he is for as long as he can remember. This can become a self-fulfilling prophecy and yet still you continue doing so despite years of teachers telling you he's behaving perfectly.
I suspect that this is because teachers tend to set age appropriate boundaries, clear and consistent rules that are fair for all, coupled with age appropriate consequences and rewards. He seems to thrive in an environment that doesn't treat him with the hostility he experiences at home (however hard you try to hide it, children can tell).
From the sounds of it, you have given vengeful parenting with retaliative punishments a jolly good go, six years worth of it if I'm reading you right. It hasn't helped. And no amount of punishment will help, because that is not what he needs, however logical your consequences may seem at the time. He is clearly understanding them as retaliation and therefore resorting to the exact same tactics you employ.
Why not try another way?
Try building a positive, open relationship with him. Bin the vengeful parenting and the OTT consequences, focus on empathetic listening and making amends. I mean have you asked him why he wants to tell his little sister that there's no such thing as Santa? Have you asked him what he wants to achieve with that? You say you've discussed his bad behaviour a lot, but do you listen without judging him or jumping in with suggestions or do you speak at him and dismiss anything he tries to say as excuses?
If you don't already, you could try holding regular family meetings where everyone gets heard, including his younger siblings. Explain the rights, responsibilities and privileges everyone has and which additional privileges the children can earn for good behaviour. Limit the number of behaviours you wish to tackle - three to five is more than enough. List a number of options for consequences and rewards, then deliver a kind but firm explanation that these specific behaviours are not what you want to see from any member of the family and draw up appropriate rules around them.
No lectures, no shaming, and please don't make it all about him. Then let the kids choose which rewards they will receive for following the rules, which consequences for breaking them and how they may make amends. Next time let the kids tell you what worked and what didn't. Adjust your rules, rewards and consequences if necessary. It isn't too late for any of that.
One last suggestion - you are clearly distressed and full of negative feelings about your son. He can feel that, he knows it, sees it, hears it. It won't motivate him to do better, it will cement his conviction that he is worthless, the black sheep who can do nothing right.
Try to make a list of everything that is good about him, that you love about him, however small these things may be right now. Focus on these things, notice them when they happen, hold onto them to tide you over the next bad situation. It's not easy to do, but it does help in reprogramming yourself.