Very concerned

Very long story short.  I went off birthcontrol in October because we were ttc periods evened out and what not but still got nothing decided to hold off for a year so I went back on birth control at the beging of this month and my period came supper early started out spotting then heavy with clots.  What I'm concerned about is I have never had this short of cycle when when I started birth control for the very first time it came when it was supposed too and I have had early pregnancy symptoms like heart burn (I never ever get heart burn) back ache, and acne in different places than I usually do, I've taken 2 test both bfn. Is it possible I'm pregnant? I've read lots that women confuse bleeding for a period and be pregnant   These are my past two cycles