Um...what do you mean by "ulterior motives"?
Do you mean you'll be hurt if the guy mainly wants a sexual relationship (or even just one sexual encounter)?
Because it kind of sounds like this guy thinks you're hot and maybe knows you're gay and thinks that's hot too.
Which all sounds great to me, but I don't have Catholic guilt!
Don't overthink things. Go on the date, get to the know guy, explain your situation and what you want, ask him what he wants.
I've heard that a lot of sex is a pretty good cure for Catholic guilt
Count yourself lucky that you are with a woman who thinks it's awesome that other people find you hot. Enjoy it! You really don't have a problem here as far as I can tell.