Help please! could i be pregnant?

Ok, so lately i've been extremely forgetful, pretty tired, getting headaches almost everyday. My period was a day late, which never happens. it is also a lot lighter than usual. today i got a really bad headache, then shortly after i got really nauseous then i threw up. after i threw up i felt fine. i took a pregnancy test on the day my period was suppose to show up and it was negative. does this sound like i could be pregnant, or anything else you've ever heard of. Ive been on birth control pills, but i have been forgetful and there are a lot of times ive had to take two at once. I also seem to be peeing more than usual