Guys help me out, why does he want to have sex with me, seriously?

It is quite likely he wants to have sex with you because he finds you are attractive and an exciting woman. It is also possible that you are the most important woman in his life and the other women he has dated have never meant this much to him. Or it is the conjunction of the stars and planets. Who the hell knows. He wants to have sex with you. If you want to have sex with him, go for it. If you are wondering if this is the romance of your life and you have concerns about going too far too fast, that's something else again. If he is really special for you, tell him so and ask him this question.