Hi hopejoy! Sorry I'm a little late, but I wanted to reply because it seems we're in the same boat... I haven't had a period in about 8 months now, and after blood tests and an ultrasound, I was diagnosed with PCOS. I was on the pill on and off for about 8 years, so I don't know when it really started, but I had been a vegetarian for about 4 years prior to that and didn't have this problem. So unless your diet is really bad, it's probably not related to that.
My doctor also suggested I go (back) on the pill, but like you said earlier, I didn't want to since I'd already been on it so long, and I was concerned that it would just mask symptoms of a bigger problem. He said that was OK, but that every 3-4 months I should take progesterone for a few days so I get a period, to clear things out. So far that's worked out OK, and the only real problem I've had is hypoglycemia (which actually improved when I went vegan earlier this year). I asked him if I would ever get a normal period again, and he said maybe not, but that it wasn't a problem unless I started noticing other serious symptoms of a hormonal imbalance. And even if you do have PCOS, it doesn't necessarily mean you'll need surgery, so don't worry too much about that part.
It definitely can be a long-term condition, though, so if you're really not comfortable with your doctor, maybe if you talk to your parents and express your concerns, they will help you find a new one. I'm new to all this too, so I don't really have much advice, but feel free to PM or e-mail me if you ever need moral support. Good luck!