Could I be pregnant?

[Magnoliablood]

I had a normal period (heavy , bad cramping , headaches , ect) , April 9-13. I had unprotected sex the 14th. He said that he came inside me but didn't tell me in time to take plan b. May 8th I had brown discharge, I thought it was implantation bleeding. It eventually turned red and lasted until about the 13th but by then it was back to brown again, but never got heavier than spotting. My periods are usually heavy. This month , June 9th , I'm having really bad cramping and all my period symptoms just as before , with the same light period, could I be pregnant? If not what is causing the light period? Im only 18 and I'm not on birth control so I know it's not that or menopause.