Thank you everyone for your responses.
DS has been an angel today, I have no idea why, I am exactly the same parent, behaving the same way as usual. He decided that today he would behave wonderfully. Lets see what happens tomorrow.
yawingmonster: I like your carseat idea. DS?s misbehavior occurs mostly when we are at home. When we are at friend?s houses he can be a handful as well, opening closing doors, touching everything, it is difficult to converse calmly. Funnily enough, DS is behaving really well when we are out now, he used to have no fear of danger (because of his GDD) and it was impossible for me to go out with him and DS2 on my own to an open park. Going out of walks used to be a nightmare, running off! But now he is fantastic and will stay close to me and obey me.
I think I need to find a instantaneous consequence that can really have an effect on him. That is the difficult bit.
KathrynAustin: Thank you! Really good to know I?m not alone. Most of my friends have girls and they always seem so well behaved!
RunningGirl: Wow thank you for that long list of ideas. Sticker charts, I tried them for potty training and they didn?t work. Maybe I should give them a go again for behaviour. Zero tolerance, goodness, I find that really hard. I think for me zero tolerance would be applicable if he is aggressive towards someone (he is not aggressive at all, he can get frustrated but he never hits anyone).
Ignoring tantrums: Oh, I am the queen for ignoring tantrums, no problem there. It is not tantrums that are the problem with DS because he knows he will get nowhere.
alardi: yes I physically intervene and take him off, but he does it over and over again. I do plenty of bonding fun things, I have to, because of his special needs I do plenty of stimulatory activities with him I have no choice really. And actually I am starting to think that I need to do less with him because he is so used to doing stuff with me that he is constantly looking for me. That was an interesting review of 123 thanks.
hoarsewhisperer and arcticlemming: Yes I think it is about finding the right approach depending on the circumstance. However, based on what yawningmonster said I think maybe the 123 approach won?t work for DS because of his special needs.
Thank you everyone for helping!