I have 3 children, aged 7, 5 and 3, 2 girls and and a younger boy. At school and nursery, I get reports of them being "lovely" and well-behaved, noone has anything bad to say about them.
At home, however, it is a different matter. They constantly fight, scream, cry, hit, trash each other's toys, trash all my stuff (eg my 5yo drew on the sofa "just because). They whinge constantly, and are always wanting things. Nothing seems to make them happy. I think my main disappointment is that they never seem to be happy, and I don't feel happy either

I think I am reasonably strict, in that there are clear boundaries, and they know what I will not allow, but they take no notice, and often cheerfully disobey me. I don't smack, but I do admit to shouting sometimes. I have made a real effort recently to stop shouting, but if anything their behaviour has gotten worse. I try to pay no attention to their whining and screaming, which is usually over something ridiculously trivial, although to hear them you would think that they had broken limbs apiece, rather than someone wouldn't move from where they wanted to sit etc.
I have tried talking to them, and explaining how sad I feel when they hurt each other and break all my things, but it makes no difference.
I try to take them places and do things with them. Today, for example, I took them to a dog show thing they were keen to go to, with agility dogs, and sheepdog displays. Within minutes they were bored, squabbling and whinging for me to buy them things from stalls- things that have been discarded or lost already. I spend time with them individually at night, reading them stories and chat to them lots. I then took them to play with friends, who they have been badgering me to play with all week. Afterwards I asked them if they had a good time, and they moaned and said no, although they did seem to be having fun at the time.
They know I love them, and take that completely for granted. They seem not to care two hoots if they have upset me, as long as they get what they want. I ask them would they behave this way at school etc and they say no, as they would "get into trouble"! But when they are "in trouble" with me, they don't seem too bothered
Why do they not respect me? I find it hard to think of ways to punish them that are meaningful to them. The only thing that has ever upset them is getting their night-time story taken away, but I hate doing that, as I feel it is an important thing for us as a family.
I know people say that "they're just children" and "all children are like that", but I remember being their age, and I would have been really upset if I'd upset my mum, and ashamed. I wouldn't have dreamt of taking her stuff or drawing on furniture at that age. Where am I going wrong? DH says I am not strict enough, but they don't listen to him either! I don't want to be a big bad mum, but I'm not a pushover! I just want to enjoy my children and for them to be happy. Any suggestions welcome, as I feel really quite down about this at the moment.