how do o talk to a casual sexual partner about safe sex?

Kat
Okay so I have maybe two hours before Im neck deep and I need advice NOW! I was hooking up with this guy a while back and he went away for a few months, now that he's back we want to start 'hanging out' again. He had a girlfriend for a bit, and on top of that who knows who he was hooking up with. How do I get him to take it seriously when I ask how many more girls he's been with and if he's std free? The farthest we go is oral, but it's still VERY intimate and Id feel a lot more comfortable doing it with a condom (which makes me sound  like a baby to him probably but I think it's reasonable). Anyways. Any advice you have for having the talk with your fuck buddy would be GREAT!