I don't date coworkers. The drama is a bit much if you two break up. So, 1) He's young, 2) he seems to want only sex, 3) so I think you're right, he does just want sex. So tell him to buzz off. Buy him a small cherry pie and tell him to have fun with it. ("American Pie" reference.)
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)