Getting off the pill

So i got off a low dosage pill back in March and i had only been on it for like 2 months and every since then my period has been irregular and very light, coming out brown or pink. Ive only had sex twice since March both times we used a Condom. The last time was in September but i got my period at the beginning of November and it was light lasting for about 6 days and it was mostly brown with some red. I was supposed to get it 4 days ago but it hasnt come. What do you think is the problem?