I had unprotected sex 3 months ago and now my periods are only lasting 2 days at the most and are extremely light. My periods are usually heavy and last a minimum of 5 days. I hhave been gaining weight and having really weird cravings. My boobs are growing and nipples are showing bigger bumps on aerola and browning. I have taken 4 HPT and they have came out negative. Can i still be pregnant?