
Wow...if you can't afford a pregnancy test, I'm betting you can't afford birthcontrol either.
Go to Planned Parenthood and get a pregnancy test done. They will charge you on a sliding scale, and usually if you have no money, a pregnancy test (and some counseling on safer sex!!) will be free.
You need to see a medical professional. There is no way anyone can diagnose you over the internet (and I'd be scared of anyone that said they could!).
I wish you the best.