I feel pregnant but my?

Nipples are really sore, I'm really grumpy, I'm tired all the time, getting heart burn and funny butterflys in my tummy. I'm gettin the occasional cramps and I'm going to the toilet like 2 times a day which is not normal for me usually its every other day. Also I'm only a size 6 and my belly is noticably bigger infact so bloated a few people have asked me whether I am pregnant??? my period is due in 5 days. I did 2 tests and both werr negative ! What's going on ? Thanks