I have a belly have pregnancy symptoms don't know how far along i am need help all test come out negative?

have a belly have pregnancy symptoms don't know how far along i am need help all test come out negative but im still geting symotoms and my belly wont go flat nemore its like getin hard i hought i was preg n january buh it turned out to b a polly cist is there a way that i am pregnant becoz im getting all the pregnancy symptomsand my belly is getting bigger n i dnt eat alot either so drinkin some water n eating a few crackers shouldnt make my belly big should it could it b pregnancy coz i get headeaches mood swings n i was constipated n january so plz help me!!!!!!