Discharge Issues? Not likely to be pregnant.?

I've been on the patch continuously (no off weeks) since November 2010, I switched from birth control pills because they nauseated me. A few weeks ago I had what I think is breakthrough bleeding. It was heavy enough to be like a period and lasted the whole week. Then I just had a lot (more than normal) white discharge. I got a kidney infection, went on medication, and now it's a lot of it, but it has a yellow tint (medication causing this?). It's driving me crazy. I think it may be a yeast infection, but it's runnier in consistency than what I know they usually are. I'm no stranger to the yeast infection. Any medication I take usually causes one. Also, it doesn't really smell normal, but not fishy.

-I don't have a STD or STI, I and my boyfriend of a year have been tested.

-I'm 20 years old

-Yes, I do have a boyfriend. We do have unprotected sex. But I've been on this patch for awhile now so it shouldn't be an issue.

Since I've been on the patch so long, I don't think this is pregnancy. I was just wondering if anyone had any ideas of what could be causing this before I head to the doc.