Help Please!!!!

I have hooked up with this guy twice and we decided that we would be friends with benefits seeing I am homoromantic.

I have had this crush on a girl for a while and she said she wasn’t gonna date me yet seeing I’m leaving for a 7 month long college internship soon, but today she asked me out and the guy just messaged me (like an hour later) about hooking up again.

What should I tell him to let him down easy?