Am I pregnant?

Hi everyone,

I'm 19. Lately I've been feeling really tired and often have short cramps lower down in my belly. I stopped the pill half a year ago because I was on a different pill that didn't mix well with it, but after I stopped the pill I had unprotected sex with my partner. I didn't get my period last December, nor in January 2014. I did get it in February, but very early. In March I bled twice (or had bleeding) – one period lasted 3-4 days and then another lasted a week. I took 3 pregnancy tests: 2 in December and 1 in January, all negative. Still, I get headaches, I'm often tired, sometimes feel lightheaded, eat more and have gained weight (that could be because of eating more). I also sometimes have mild pain in my lower belly during sex. Lately I've also been having shaky legs and a gurgling stomach.

Am I pregnant after all, or does anyone know of something else that could cause these symptoms?

HELP ME, thanks in advance!