Honestly, you needed to clarify what he meant before you went off on him. F*&$ing with someone doesn't necessarily mean sex. In my country, it can also mean messing with someone's head to deliberately upset them. Having said that, f*cking with someone whether it means cheating or hurting/teasing them is an awful thing to do. Do you really want to be with someone who would do any of these things?
How old are you? Have you ever met him face to face? If so, how much time have you spent together? How long has this "relationship" been going on?
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.