has anybody got pregnant after taken plan b?

Suzanne
I had sex last week on the 9th and he came inside me. I found out after I was ovulating and took the morning pill the next morning. I have had dark brown black discharge or blood the last too days its been a week since I took the plan b, I also had cramps before I started bleeding. I want to know if anybody had these symptoms and found out they were pregnant. Ian not suppose to start my period for another week