Birth control pill/weird period...Serious answers only, please!!!?

[::bren::]

I’m on the pill. My bf was coming home from Iraq and I was due to start my period at that time. So I went straight into a new pack of pills during the week of the reminder pills to throw off my period. Which works. I’ve done it one other time about 7 years ago. However, this happened 2 weeks ago and since then I’ve had this stupid “old blood” kind of spotty period. It’s not a period…just this nasty dark stuff (old blood). I have a doctor’s appt scheduled for Monday, but was wondering if anyone knows what this is. It’s certainly not enough to fill a tampon in a full day. It’s more annoying than anything b/c I’ve had to wear one every day for the past 2 weeks and can’t exactly have sex b/c it is sort of embarrassing if it gets on his part. Not to mention gross. It doesn’t have a flow, it’s like old blood that is in there.