birth control side effects or pregnant?

So I've been taking a combination birth control pill for two months now , it's a pack that you take for three months and on the last week of the pack (yellow pills ) is when I have my Period , I just started my first week of my last month but I've been afraid I was pregnant because me and my s.o have had unprotected sexa few times and he does not pull out . I get sick every time i start eating something although i do not throw up , I've only thrown up once . My breast have been very sensitive . I'm tired all the time and always have head aches  . I've been bleeding very thin pinkish/red blood every day for almost two weeks now .  I've taken two pregnancy test each two weeks apart but they both came out negative . This is my first time ever taking birth control so I'm not sure if it's just side effects or it's pregnancy ? Somebody give me some input please ..