afraid i may be pregnant


i had sex april 28th, my boyfriend did not come, when i asked him if there was any precum, he said no. on may 5th (eight days before my expected period) i experienced slight pms symptoms which included a dark brown discharge, with a little blood. the next days i just had brown discharge no blood. im not sure if this is implantation bleeding or early pms bc brown discharge is normal for me before i have my period. im not sure how long my cycle is. but if it helps i recorded that march 7th & april 18th were the two start dates of my last two periods.