My period was on tuesday of last week, i had intercourse yesterday and whenn he pulled out he had blood on his penis. what could be wrong?

Leftover blood: It is fairly to common to have some left over blood in the back of the vagina after your menstrual cycle. When you have sex while the blood is still there then the man may see it on his penis. This is the most logical explanation. If you continue to have irregular bleeding or if he begins to bleed from the penis then schedule a visit for follow up.