Sexually inexperienced...

[MikeW]

...I knew I had to explain. He thought it was because I was uncertain about having sex with an older man and was relieved and not horrified as I had expected him to be. ...

Congratulations. I'm happy it was a positive experience for you.

I hope this is a lesson in communication as well. People can often 'sense' when someone else is feeling uncomfortable. What they may not know (and thus only be able to guess at) is why. IMO, it is a good idea to open and honest with people about things that are important to both of you. This is just one example. As someone else said, if he was going to reject you for lack of experience, then he wasn't the man you should be having your first experience with.