Pregnancy

The last time i had sex was june 21 before he went to bootcamp. He and i havent been apart since we've started dating 3 years ago and its already been 4 months since he's been gone and things have been really hard lately. Since he has left my periods have been irregular and short. They normally last about 4-6 days and heavy but lately theyve been 1-2 days long and very light. Ive been looking bloated lately. But i have no other pregnancy syptoms. Food nauseates me sometimes. And i get full off of two bites of whatever i eat. I have taken 3 pregnancy tests since july and all of them had said negative. What do you guys think? Should i go to the doctors?