Is it ok to have sex on the first date?
I think it depends on what you're aiming for, so to speak. If you are really desperate for physical contact, and haven't touched anyone other than yourself for several months, this might be the way to go. It could, however, sabotage any long-term hopes you have with another person. The best thing to do is to wait and get to know someone if you think you might like to be with them for longer than 24 hours.
Sorry to break it to you,