Gaining mean pigs trust or something

Question
Hello My male guinea pig is untouchable, he didnt like being bothered since the day I bought him t the age for three months, and for awhile now I cant even pick him up without putting a light towel over his head to avoid being bitten. If I catch him and let him out for exercise then I try to pet him he twiches, twists and runs like I'm going to kill him. He used to chatter his teeth at me, I havent heard him doing that in awhile, He had a knot on his rear end and I clipped it off yestereday after much struggling to hold him. He runs in his sleeping box when I come near and it takes me a good five minutes to catch him to clean his cage, I would like to keep him but I have to be able to pick him up without his trying to bite me, if you can give me any advice I will aprecate it very much.  

Answer
Sorry for the delay in response.  All Experts was having a problem with a time out each time I tried to send my answers.  So I had to wait until the problem was fixed in order to get back to you.

The best way to do this is to offer him a snack and a gentle touch or pet before trying to pick him up.  Also, be very quite and don't startle him when you go to pick him up.  The chattering teeth and etc are normal for a cavy.  Just one of their many sounds and actions.