Swollen abdominal! Pregnant or weight gain ?

I took two pregnancy test after my period was 14 days late. They were both negative...but my lower stomach has been a bet blowed "bigger", it seems after about a week after I've token the tests. I've been feeling really fat, very insecure about my body lately. I don't know if I'm just gaining weight or if the pregnancy tests were both wrong???? Need a woman's opinion!!