Casey has the right idea on the bottles but now to the sleeping in his own bed issue. When your son wakes up, instead of letting him crawl in with you, you go with him to his bed. If he has a toddler bed or crib then sit on the floor and hold his hand til he falls back to sleep. If he has a regular bed, definately crawl in bed with him. The first time you do this he will probably wake up again bout an 1-1/2 to 2 hrs later. So maybe stay with him til he sees you're still there and then go back to your own bed.
Given some time (all kids are different so how long/short will be different, too) with this and he should then be able to fall back to sleep himself with out waking you.
If he is afraid of the dark and thats why he needs you, use a small night light. If he is afraid of the monsters under his bed, make his favorite or even a new stuffed animal his protector that will scare the monsters into the next town. I also use the "make your own dream before you fall asleep" trick. If it's nightmares, then have him think of you chasing away the monsters in his dreams. All these worked for me.
Good luck!