How do I qet him to finally ask me out ?

Well, I think that you s hould try going out with him, but I personally think that he's going to you as a last resort. But you can blatantly state it, and it might work, seeing as after he found out you like him he flirted with you. Still, I think that if he REALLY liked you, he'd have gone to you instead of the the other girl. I tried. Do with that what you will.