Feeling Like A Bad Mom

Lately I've been having a hard time with L. My patience for his antics has long since worn thin. Let me try to explain a few of the things that he does.
He constantly complains about anything and everything. Even when something hasn't happened yet, but there is a small chance it could, he moans and whines about it.
He doesn't listen. I tell him to do something, and he ignores me. Until I threaten him with taking away something such as his iPod.
He has a hard time getting along with the other kids here at home. He can't seem to make compromises, and when things don't go his way, he throws a fit, or he lashes out physically, or he does things to deliberately annoy them.
He argues with me, his brother, anyone, and he slams doors.
When he has things that don't go his way, or he gets hurt, or he is asked to do some kind of chore, it's a huge drama. It's the "worst day ever" or he wants to "die" or "kill himself" or he "hates this world". I don't know how to take that. DoI take him seriously and get him professional help? Is he depressed? Or is it a ploy for attention? So far I've tried to ignore it, but I don't want to ignore something potentially serious.
Everything is boooooorrrrrrriiinnnggg.
When he gets into trouble, he hits himself in the head and calls himself stupid. I can't seem to make him see that he's not, no matter what, and I want to know where I went wrong with fostering his self-esteem. Who has told him that he is stupid? He feels inadequate next to all the other kids at school.
Things are bad. I want him to be a happy child. But he makes it seem like his life is a total hardship. I don't know how to show him that he has a great life. That he's so lucky to be him.
The worst part of all this is that I don't want to be around him anymore. When he screams out, "I HATE THIS WORLD!!" it takes everything in me not to tell him to leave then. The comments that go through my head when he is being irritating are shocking even to me. And while I realize that I shouldn't be saying (I don't) or even thinking those things as his mother, I can't help it. It isn't until later when I calm down significantly that I feel a little bad.
The other weekend, after saying at least five separate times that the floor was wet (freshly washed) and to stay off, I lost it. He walked onto the floor while having a fit because his brother got a lemonade and he never asked for one, to dump out the drink he did have. Aside from the fact that he was wasting something out of spite, I was very angry that he was on my clean wet floor! I screamed at him so loudly that A) I'm sure the neighbours heard, B) I made my throat hurt and C) I startled him so bad he started to cry. You'd think I would feel bad for that, but I didn't. I was seething, my blood was pounding through my veins, and it was only by a slim margin that I managed to say "Go to your room!" instead of "Get out of my sight, I can't stand looking at you!"
Because that's what I was thinking.
After a 20 minute walk around the neighbourhood and a small stay in my garden, I finally felt calm enough to go back in the house. I was still angry though, but forced myself to go to his room and try to make amends.
I know this may seem an extreme over-reaction to you, but this is an ongoing thing. It's a culmination of one misbehavior after another. I can handle not listening. I can handle whining. I can handle mess-making. I can handle complaining. I can handle (some) fighting. But I can't handle ALL of it, ALL at once, ALL the time.
I feel like a bad mother. I don't know how to fix it. I don't know how to make him happier. I don't know how to make myself want to be around him. And I'm scared that one day I'm going to say or do something I'll really regret.
I think the main problem now is that there's no reward. You know how you say, "It's all worth it" when they give you a hug, or kiss, or sweet smile, or say they love you out of the blue?
Yeah, there's none of that. He won't hug me unless I steal one or ask, he NEVER gives me a kiss, the only I love you's are when I day them first and that's few and far between. There's not a lot to keep me coming back for more. Right now, to me, he feels like another kid in my daycare who annoys the hell out of me and hasn't got picked up for days! Even my babies give me more love than he does.
So here's my next question. Do I continue to "force" physical affection on him/from him, or do I leave him alone? Am I disrespecting his personal space or wishes by hugging him and kissing him when he clearly doesn't want me to? Or is it my right (because really, I think it is)?
What do I do? School is done in three days, and honestly, I'm worried. I'm worried we'll have a crappy summer and I'll end up mentally ill or something.
Right now he is in bed. I am thinking back on my day, and analyzing it. Today, I really tried to keep my cool. No yelling. I did pretty well. However, I ended up crying instead. I was chopping rhubarb and couldn't stop the tears from falling as I was feeling like a horrible mom for wishing my kids away. Luckily no one noticed, as I couldn't really explain it.
Sigh.
I just can't win.