My recommendation is to trust your gut. I do not advocate abstinence, by any means, but if you don't feel comfortable, don't do it.
There are more guys in the world than any gay man could ever hope to shake his dick at. So just go into it knowing that anything is possible, and hope for the best. But, if he doesn't feel right, there are plenty of other guys to get through.
I like to listen to the song "Til I Get To U" by Nika Costa when I'm feeling frustrated about dating. It just affirms that one must naturally make many mistakes before getting to someone who is right for you. As Dan Savage says, "every relationship that you are ever in WILL FAIL... until one doesn't."
Keep it low-pressure and honest, and I'm sure you'll have a rewarding experience with this guy. Good luck!