Whether to be worried or not

I've been taking the pill since I was about 15 because my periods have never been normal on their own and I'm now 18. I've been on the same pill for a couple years now . I'm currently with someone and we have sex quite often (not complaining), but a couple weeks ago we had sex with no back up protection and he happened to cum in me. Now this week I've been bleeding like my period, but I still have a full week till I'm actually supposed to have my period. I don't know if I should be worried that I may actually be pregnant or not, or if it's just a random kind of thing. Especially since I'm bad with the pill and often take it at different hours