What could cause this??

Just had period 2 weeks ago, I'm on birth control but I have only been on it a month. I've been having unprotected sex with my boyfriend for the last month. He's questioned his pull out game, I have been experiencing this and brown discarge for the last few days. I have been quite emotional, and have had bad headaches every day. The odd thing is for the last 2 days I have been bleeding a little after sex. Please help!!