Will plan b mess up your period cycle and for how long?

so me and my boyfriend had sex and he accidently cummed in me, thought the condom was on. But i toke plan b asap and a week after i toke plan b i think i had my period? i dont know but i was bleeding with blood clots. now the nex month im like a week late now? what should i do ? i also toke 4 pergancy tests and all negative .. help pleaase