please help my boa wont eat!

he hasnt ate in 2 1/2 to 3 months and i dont know what to do.
i've had him about 5 months he use to eat fine, but i sold him to a kid and he brought him back after two weeks and said he would'nt eat!
he just shed aweek ago, but still hasnt shed all of his head yet!
somebody please tell me what to do!!!!

Please tell us about your setup,, temps, cage size, etc.

Have you tried live feeding yet? If the problem isn't from your setup. I don't think it would be. You have housed this snake before with out issues. A live feeding may be just the thing to get him back into feeding.

Welcome to Herp Center
It sounds like the snake has been through a lot of change and stress. Perhaps the kid you sold him to did not keep him adequately housed/heated etc. That could also be why he's having a bad shed.
Don't panic about the eating thing yet! Deal with the shed first:
Take a hand towel, wet it with warm water and wring it out really well.
Put the snake and the towel into a pillowcase.
Close the pillowcase and put it in the snake's enclosure (not on the hot side)
Leave it in there over night. By moving around inside the pillowcase against the damp towel, the rest of the shed should come off.
Take the snake out of the pillowcase.
Then LEAVE him alone for 2-3 days to relax and re-adjust to his new home. He will not starve! Make sure he has plenty of fresh water and an appropriate heat gradient in his terrarium.
Whatever he was eating before, he should eat again. When you're ready to feed: make sure it's dark in the room. If you feed F/T make sure to heat it up well, with a heat lamp or hairdryer. Use feeding tongs and wiggle it around. If he doesn't take it, leave him alone with it for a few hours.
I personally don't recommend feeding live, especially for a snake who is not eating. The mouse/rat can cause some VERY nasty bites to your snake. If you have live food, it's better to pre-kill it just before feeding. (put it in a bag and whack it hard against the edge of a table). That way it can't hurt your snake if he decides he's still not hungry.

Be patient. Snakes can go for a VERY VERY long time without eating.
Some health issues to look for:
(When he defecates, you should take it in to a vet to have checked for internal parasites.)
Also, when the shed is off: look at the snake carefully. Does he have any bubbles coming out of his nose? Does he breathe with is mouth open? Does he lie around lethargic? If he has any of these symptoms, he could have a respiratory infection and probably won't feel like eating until that is treated. You'd have to take him to a vet to get antibiotics.
If he seems healthy, though, just BE PATIENT. If he doesn't eat this time; leave him alone for a week and try again. If you try every day over and over, he'll just stay stressed and definitely won't want to feed.
Good luck!

I second what BlackJack said. take care of the shed first, let him settle back into his environment and THEN try feeding again. Good luck!

Are you staying in the room when you try to feed? It's possible the kid who had it for a while did something to frighten it and it doesn't feel safe eating with you there. After you get the shed taken care of try leaving the DEAD prey in with the snake for a while and leaving it alone. Maybe even cover the cage.
IMO going back to feeding live should be a last resort.