Ay anak, the best way to know for sure is to take a pregnancy test or go see your OB-GYN, kahit irregular ka, peace of mind lang yan worth it talaga. Since may unprotected contact kayo, it's possible, pero the pintig and worry could also be anxiety, lalo na kung irregular period mo normally. A few of my mum friends had the same worry, and honestly getting tested was the quickest way para ma-ease ang minds nila. Hang in there, whatever the result, your doc can guide you properly.