I have a brown discharge... :S?

I have had a very light discharge a couple of times before. It lasted like only a day and was only enuff to see it when i wiped, after just the one day or so I would get my period. I had the same discharge about 3 days ago, where it was only bad enuff to see when i wiped. It went away, I thought maybe it was a false alarm for my period; last month it was a little wonky and I shouldnt get this month's for another coupla days. Then it came back today but it's heavier, I've had to wear a pantyliner all day. The other night when it had gone away, I used some summers eve cleansing wipes and my bf said it smelled diff but not better he said it smelled "bitter". I'm paranoid; I always think it smells bad. I am on birth control (orth tri-cyclen lo), and friend have told me sometimes that happens, but theyre not on the same meds and I've never had it this bad. I can't douche; every time I've tried it gives me a yeast infection. I don't think it's a yeast infection or a bladder infection or a uti or anything, and I'm pretty sure I'm not prenant but it's bothering me, gettin kinda worried.