cramping

So I knew my period was going to come today but I haven't seen my boyfriend in a while . So I started taking my birth control Saturday and Sunday . Now I have horrible cramps and lower back pain ? Is that normal? Also almost 2-3 weeks ago we had sex but the condom slipped off his dick and was inside me ! . So I don't know what the cramping could be since I read online cramping can also mean your pregnant ? Help me please ?!!!😭😭😭😭😭😭