How old are you?
Have You Met this Guy?
Have you ever actually met this guy?
Basically, though you have been communicating long distance, you don't actually have a real relationship. I would never make my first sexual experience such a potentially disastrous one.
Call me corny, but for the first time, you should be in love, and be able to deal with the consequences of sex with the person for some time afterwards.
Sex Changes Everything
Sex changes everything. He's lying if he tells you otherwise. It's not that you'll look like a slut, you'll feel differently. You'll feel differently about him, about yourself, and maybe even about the world.
It's a big deal, your first time. I think you should wait until the future with█a person is more real. Obviously, it's your choice. I've made some good█choices and some bad ones in the past. But, I don't think it's as simple as "if it feels good, do it."
Especially the first time.