Ok well me and my boyfriend had unprotected sex?

and we didnt want a baby. 3 weeks after (today) i got bad stomach cramps period pains. when i got home i went to the loo and there was no blood leakage anywhere and then a massive lump of blood fell into the loo. and now it is very very pale pink everytime i go to the loo. is this normal? i have experienced the first day of my period to be very light before and then the next day very dark but this time its like nothing at all is coming out. im not pregnant am i? coz if i am i cant tell my mom:( x