Sex on the fourth date - blow out disaster please advise!!!!?

Well, here's the thing, you're allowed to go for whatever you want at any point in the dating process...and the other person is allowed to tell you to back the Hell off. Some girls will do it on the first date, some on the fourth some after months and some not until marriage. It sounds like you had some great dates, but didn't spend enough time learning whether or not you were on the same page sexually. Turns out you're not. There is no hard and fast rule that says when sex will happen. Better luck next time.