Help!!! 😣

Okay hello, so im kind of freaking out here just a bit. I had sex with my bf and he cummed in me unfortunately and we didnt have protection... a week i believed passed by and i went pee and noticed heavy amount of blood in my underwear a dark color it lasted i believe 1 day and it stopped.... and i havent bled since my last peroid was December 25, 26 and 27 or what I believe to be my peroid.... I looked online and I was bleeding like my normal peroid but I read that the way implantation works is it's 1-2 days and my peroid is 2 1/2... I'm not sure whether it was really my peroid or not (it consisted of dark blood too I'm not sure if that makes a difference or not just thought I should say that too) anywho I was suppose to get my peroid today but haven't I also have been having cramps for the pasted 3 days and it has been off and on also everything else has been regular not abnormal .... I'm scared and not ready to be a mother I know that it my fault for not being careful but please help..... any advice would help me!!