Is it my period or not?

So I am on birth control, and my first pill was on the 5th of this month. Me and my boyfriend has sex that day. A few days later I missed a pill, and took two the next day like my doc told me. On the 14th I noticed light spotting. Darkish red. Then it kinda went away, then it started again the 16th. It got heavier, then stopped on the 20th (still regularly taking my pills). Me and my boyfriend had sex yesterday and I bleed a little afterwards. Today, it was like murder, and my cramps were so bad I couldn't get out of bed. What is this??