HELP!! My 3-Year Old is Turning Me Into a Zombie!!!

My son is almost 4 (will be the beginning of December) and he is literally turning me into a zombie! From the time he started walking, he has walked himself to our room, and crawled into bed with us at sometime in the middle of the night. At first it was cute, but now it is driving me mad! I purposely keep myself up until after midnight in the hopes that he will fall asleep in his own bed, and when he does, I sneak upstairs, trying not to wake him. But like clockwork, at 3am there he is.
We have a king sized bed, but when your son sleeps sideways, it doesn't really matter how big your bed is. To make matters worse, he's been going through this I want mommy to do everything phase for about the last 2 years, so he sleeps as far away from his dad as possible. That leaves me with a tiny sliver of the edge of the bed to try and sleep on. So, I spend what's left of the early morning hours hanging on to my sliver for dear life. Let me tell you, it's tough to get any sleep, knowing that you can fall off the bed at any moment.
And as if this wasn't bad enough, this morning I woke up laying in pee soaked sheets. This was very ironic since we were up until well after midnight listening to my son scream at the top of his lungs because he wanted his cup. My husband and I have stopped letting him take a cup to bed with him, as we are trying to potty train him (that's not going well either), but apparently he found a drink somewhere.
So, I am desperate here. Am I the only one out there who has gone through this? Can someone please give me some good advice on how to get him to sleep in his own bed? And while your at it, how the heck do I potty train him? You can see my previous post on this issue; he is so stubborn!!
Many many thanks in advance! :)
~Dana~