I got the contraceptive injection last Monday, just today I've been having super bad cramps and I feel so tired. Just before I went to pee and when I wiped there was really light blood. Is this the uterus lining or what? I'm so confused because my period isn't due until the 31st of this month. I should also add that I had sex on Saturday and he came inside of me (I don't know if this will impact or not). I ovulated just today also. Please enlighten me xx