Please comment and help!

I have been light headed and having headaches. I haven't had sex since Jan 20th. I was on birth control, used condoms and withdrew. I got my period Jan 22nd (on time). I got my period again on time for on Feb 18th. 6 days before though I took a pregnancy test that came back negative. Also I stopped using birth control and five days after stopping using it I got a period. Please help me im so stressed. Please comment.