Bleeding after being came in

Tia • Full Spectrum Doula ⛑ Future Midwife; open-minded & outspoken, fitness addict, and proud vegan & naturalista 🌱
I had sex for about two weeks straight without a condom, and two of those times he came in me. After the second time the next day I started bleeding, and cramping. I know it is possible for an irregular period, but my period hasn't been irregular for years now. I had my period nine days ago. Anyone know what's going on?