Negative HPT's. Spotty periods. TMI

Okay, so I'm on BC (ortho-novum, a pill), 18yrs old, and my S/O and I are sexually active. We use condoms 99% of the time, even tho I'm on the pill. We had a bit of a scare in February this year and I immediately took a Plan B pill (condom broke before he finished -inside of me- and we didn't notice it until it was done and over with). Well last month my period came a few days early. I wasn't worried about it. But it was more like spotting with old blood and lasted only a max of 4 days. Then about a week later the spotting happened again and lasted 2.5 days. I took a hpt and it was negative and the next morning, I took another with the same results. Well my period just came this month really really early and it was light red, watery, and slightly mucus-y. It lasted 3 days again, ending with old blood. I plan to take another test tomorrow. Is there any chance I could actually be pregnant, even though I'm seeming to be spotting? I know it sounds stupid and paranoid like. But I've heard of people going through the same thing and actually being pregnant (results from HPTs and her doctor). Any ideas, thoughts, or suggestions are welcome.