HELP!

Okay so my depo shot ran out October 13th.. I decided to stop the shot because I heard how it could mess up my body. My boyfriend and I have had unprotected sex multiple times.. & he finishes inside me... (We're not nessisarily trying but we're not preventing either, since I've read everywhere that it takes a while to get pregnant after the shot.) well for the past two days I've been feeling flutters in my stomach !! And I've had a bubble feeling before and gas followed(tmi) but this time gas didn't follow ! So the first time I just let it slide but now it keeps happening? I've had a child before so I know how the flutters feel and they feel the same way .. I took a test last week and was negative , what could this be?