have alot of questions!!!!

ok to start it off my boyfriend and i had sex after my period last month.. i got on birth control right within 2 days after that.. i havent missed a pill at all.. i use to be on birth control over a year ago and stopped taking it. i rememeber taking and it not making me swell up. and all… my pants arent fitting at all… like i went from a size 3 up to a 5. my old jeans.. ive been having really really bad heart burn where ive ate a bottle of rolaids in 2 weeks. im getting full over nothing.. my stomach could be growling, as soon as i eat i get full with in taking a few bites. this morning i ate 5 mini mini muffins and i got extremely full! then a hour later im hungry again. my boyfriend has been saying ive been moody lately. i cry over nothing. he’s even noticed that im gaining a little weight.. ive taken my last birth control pill. ive been told you can still be pregnant even on the pill. my mother was with me. i just want to know if the birth control could be causing this or if i could be pregnant. cause there is a chance there as well. i know the only for sure way is to take a test. please if any one could help let me know… thank you! ~much love~