spotting between periods. Pregnant ?

so I have been on birth control since last May 2015 and i missed a pill on January 1st and I took 2 the next day I remembered . I'm normal with my period but I have been spotting since last Saturday a week before my  period . today is Wednesday and last night my husband and I had sex and now I have blood clots . do I am pregnant ? or why is this happening? thanks in advance .