Tony knew it was a bad idea to start sleeping with Steve. It could mess up team dynamics, make things even more awkward between them in the future, or just plain get in the way of their trying to save the world. Tony foresaw all of the above but not the advent of feelings, and at the most inopportune moment.
Steve knows that Tony has feelings for him and, since he doesn’t return those feelings, has been mildly dreading the day that Tony decides to do something about it. When that day finally arrives, Steve discovers that Tony’s wooing strategy isn’t anything at all like he’d expected.
Less than a year ago Tony’s biggest problem with Steve was figuring out how they could coexist in the same team without throttling each other. Now Tony’s biggest problem with Steve is making sure that the guy doesn’t fall in love with him.