I started the pill 3 months ago and was a bit apprehensive about its effects as well. I had PMT before I went on the pill and now I don't notice anything. My mood has improved. I do get headaches from time to time which I didn't get before but they're not bad. To be honest I'd rather put up with a few headaches (providing they're mild) than find myself in an unplanned pregnancy. A friend of mine is taking the pill just for heavy periods and she thinks it really helps. It does reduce blood flow.
Heres a site which tells you about one of the pills and there's a list of side effects at the bottom but I haven't really experienced any of them. I think it really depends on your own body. Maybe you could try it and if it makes you feel bad then speak to your doctor and come off it or try a different pill that may suit your body better.
link Hope this helps :)