but first he wants to have sex to get closer...i dont understand this...
if he realize that things wont work out after having sex then wht??..i wont b able to move on....
I don't understand it, either. Ideally, sex is a step you take when you are already close to a person. It's a big decision, as it can have huge effects on your emotions, body, and relationship with the other person.
Having sex with someone who doesn't already feel close to you, or who is trying to persuade you that sex will bring you closer really rarely works.
You've already foreseen the problem - if you have sex and he decides that's all he wants (which, I'm sorry to say, is what it sounds like), you're stuck with a broken heart.