My partner did not ejaculate in me and my period is on time this month, could i still be pregnant?

My partner and I started to have sex, but I stopped him because i was not ready(condums, birth control,etc.) He did not ejaculate in me, but we are not sure about if he had precum. My period during this month came exactly as it did last month;therefore, we assumed that i was not pregnant. I've have been reading preganancy experiences from other women, and they ended up still being pregnant. I do not know if my bleeding is implantation bleeding since first three days it started out not too heavy, although normal amount for me, but now im hoping that because the period could be ending soon, the fact there's practically no blood now, but a few spots of red(not pink or browknish) would be normal and meaning im not pregnant. But i must know that if implantation bleeding is normally like my situation. I really hope for that I'm not pregnant now, im not ready.