Asexuality is extremely rare. Chances are he is homosexual, and just using you as the girl to show to mom and dad, or sleeping with another girl, while still the exact same thing. Confront him. Make an issue out of it. Best to find the truth about it now. In the rare case it is asexuality your options are limited by what you want. If you can live without having the sex more power to you and carry on. If not its time to move on.
Really short but the only one I found.
http://www.totallynsfw.com/videos/videos_barbie_cummings_blows_the_state_trooper