Rugular Periods, gaining looking pregnant..

Ok so here is the deal.. Everyone month I think I'm pregnant.. ( i just worry like that ) my boyfriend and I always use condoms.. we dont have sex without them, but they have broke in the past and I have gone and taken the Plan B pill. I have had to do that 3 times because of condoms breaking, the 3rd time I took a new kind (about a week ago) my friend has had to take these as well, where you take 4 birth control pills and then 12 hrs latter you take 4 more similar to the Plan B pill just with more pills. It is what the doctor gave me, but i was still freaking out cause there were so many pills to take. Well, I have my periods the begining of every month just like always, never late if anything they are a few days early, and they are always so painful and they usually last from 5 days to 7 days, but during the times between my periods.. i feel so pregnant! My belly looks like i am, i only weight 105 pounds.. i dont gain weight, if i do its only like 3 pounds.. I already had my period at the begining of this month (Jan) and it lasted a full week and was very heavy, I haven't had another period yet because it isn't Feb yet, but i was wondering could i be pregnant and just now know it? I worry about this all the time! Please someone tell me im fine and have nothing to worry about so i will just get over it and tell me i am gaining weight around my waist because i am a lazy college student who just needs to go to the gym! lol