Dull throbbing pain in left testicle

I've read all the stuff everyone has put up about aches in their testicles but I've actually been to the doctor so many times it's just awful. I first went because of this dull pain in only my right testicle which had been driving me mad for a month. The problem is there's no swelling, no lumps, obvious veins and no redness. On checking it out he said it looked fine but it could have something to do with chlamidya or ghonnerhea (however you spell it!) - I had none of the other symptoms for this. But I was checked twice and each time was in the clear. After taking the anti-biotics (which apparently also deal with epididimitis) for these as a safeguard the pain went away on both occasions. But it keeps coming back and there is a distinct pattern - a month or so of it, nothing for 4-5 months, and then it repeats itself. In addition to this every so oftne I get e avery sharp and constant 30 minute pain about 5-10 minutes after ejaculation. I tried linking it to something but all I could really think was beer. However, when I confronted the doctor he just siad don't drink it then. But could this actually be the cause and why? It is too infrequent to accurately tell and I have had it once or twice without. It's very diffciult to plan whether yous should avoid drinking... It is driving me round the bend!!! Please someone help me.
Thanks!