Blood on toilet paper?

Okay so I'm 17 and the past two times I've had a bowel movement, there has been a little bit of blood on the toilet paper. I didn't notice any blood in my stools at all, and there isn't a lot of blood on the toilet paper either; it's kind of spotty. I'm a little scared because I've had stomach issues in the past -- I tend to be a little irregular as far as bowel movements go, but I've seen a GI doctor and I've had a barium swallow and abdominal ultrasound and everything is fine. I also have hyperthyroidism (and I just found out that my numbers are slightly high, so I'm increasing the dosage of my medication from 10mg a day to 15mg a day). I feel very warm right now, almost like a hot flash, but I just took my temperature and it's right at 98.0�. I am going to my GP on the 18th, but seeing as everything with my GI doctor has checked out completely fine, do I have to be extremely worried? I've had minor stomach discomfort for the past few days, but that was normal before too. Please help