Oh sweetie there are more people out there (both male and female) "tainted" then not. Stop doing the deed with the guy and tell him your faith and your feelings for God. His response will tell you if he is even a possible life long mate for you....God will make this clear to you...just listen.

I have been in your shoes and still am. I became a Christian after I had already moved in with my boyfriend. Once I became a Christian he understood that I could no longer have sex with him although he does try on occasion. I just recently found my own place and will be moving out of his house in the next month. He is a WONDERFUL person but is not equally yoked with me and I know our end is soon. If he doesn't love God the way you do it will never work.

Have faith in God! He will see you though this no matter how hard it might be. The person you are to be with will understand you indiscretion. God will bring you to the one you are to be with.