Wow! from your first post I estimated that you were a teenager...
So a new guy has turned your head? Wow, yippee skip, good for you.
I agree with everyone else that has said that he is (I prefer was because I believe you have blown it with the new guy) interested but isn't a cheater therefore doesn't want to be the cause of a rift between you and your partner. Doesn't someone who has spent 15 years with you deserve better than this?
To clarify my brackets above, I think, from what you have written that this guy was interested and was happy to admire you from afar. Your text has shown him a side of you he wasn't prepared for and he doesn't like. Well done!
'People are never perfect but love can be. People waste time looking for the perfect lover rather than creating the perfect love' - Princess Leigh-Cheri from Still Life With Woodpecker.