I've been on oral birth control for two years now and every once in a while I will spotbetween periods for a few days and it'll go away.

I took a week supply of antibiotics (Amoxicillin) during the first week of Feb for a tooth problem I had. Everything was fine. During the second week of Feb I got a root canal, and ended up going a week antibiotic free, then I had to take another weeks worth of Amoxicillin on the third week of Feb because my tooth had a small infection. 

Starting last week (tuesday), I started spotting (bright red) but just dismissed it as it having something to do with all the antibiotics I had taken within the last month and a half. There is no way I'm pregnant as we used a back-up method for almost two months (due to me taking antibiotics).

It has been a week now that I have been spotting (between my periods) and it has no sign of stopping. I've had cramps (not all that often) it is little to moderate flow but enough for me to use a pad all day (I have not used tampons at all).

Can me taking antibiotics cause this much spotting or is there something else that can cause this much spotting?