What Causes Flutters In Abdomen And Weight Gain With Negative HPT?

I am 21 years old and I have always had really bad cramps and heavy bleeding, my mother also has this as well and just recently she had to get the lining of her uterus burnt to help with the bleeding. Well when she was pregnant with me she said she was bleeding heavily throughout the pregnancy around when her period normally came. And Im just wondering if some how its genetic. I dont know if I am pregnant, me and my boyfriend have unprotected sex with no pull out method everytime and just recently I have gained weight and my back and ribs hurt from time to time..and I dont know if the movement in my stomach is fetal or gas. Every pregnancy test I take is negative..I am clueless???