Adam won't ask you out until the very end of the game (after the usual ending; when you return from Christmas break), but getting Carlos to come out to you early is a requirement. If he doesn't, then you can't get the ending.
You also can't be dating anyone else throughout the entire game.
It sounds like you're not getting close enough to Carlos if he isn't coming out to you. Spend more time with him and Adam, but avoid the four freakout points.
(The James conversation is fixed if it hasn't happened yet, so you might have some luck doing it sooner at a time when you can't otherwise spend time with either Adam or Carlos.)