Julie,
If you lie about your past, it's going to come back and bite you later on. Same for trying to evade issues. If this is a short term, casual relationship, you owe him nothing. If there's any chance of love developing, you have to tell him soon. If you don't tell him, or if he finds out some other way, the relationship will never recover.
Also, I don't know if you have had "relations" as a female yet, but it might be a lot easier if your "first time" was with someone who knows about your situation and cares about you.
