First of all, I'm 19, I'm on birth control, and have been for about 7 months.

I've been getting unfamiliar symptoms lately.

Nausea, fatigue, larger nipples, headaches, heartburn, and a slightly late period.

I keep thinking about the fact that there's still a very small chance of pregnancy even on the pill. Should I trot out for a test? Or stop being paranoid? What else could this be?

I would do a test. Birth control is effective but not all the time, there are a lot of times girls get pregnant on birth control. Missing on or even timing it different can get everything off. Then again you could be having pains like that before your period or getting off it that will cause those types of symptoms too. I would take a test to be reassured though.

You should test using first morning urine. There is no form of birth control that is 100% effective. There are women on this site who used 3 forms of contraception and still got pregnant.