Most Helpful Guy
It really shouldn't matter, and he doesn't really need to know. I assume you guys aren't really even dating tho? Just spending time?
Once you start dating, and you have feelings of uneasiness, or wanting to take it slow, you should be open and honest about it. Chances are, you may be shy about stuff or not know what to do in certain situations, because you've not had a boyfriend before.
It's never a good idea to hold out information to a person that you are with or are thinking of going to the next level with. Eventually it will come out, but it's always nicer to have all the information up front. If you both care about each other, you should trust him, and he should understand, and you should both be able to work it out.
Only you can figure out when to tell him. But as a guide, if you decide not to tell someone the truth because you're scared... it's probably the wrong move.
#1 rule in a relationship: If it's the right thing to do... never act (or not act) on something in a relationship just because you're scared of what might happen. This is just standing up for yourself and respecting the other person. It's something very important in a relationship.