When I read your description, and look as Angel's expression, I can't help but think he made some lewd gesture, mostly as a joke, thinking Fluttershy would never understand his pantomimes anyway, and now he's going, "Wait, what?!" that she actually seems agreeable to it. Question is, did she really understand what he was suggesting, or did she interpret it as thinking he wants to go make tea or something?
My impression is that Angel is scared shitlless about something. I am not sure why. It's the eyes. They don't look calm, perhaps it's that extra line around the eyes (buniess don't really have eyelashes, I think)?
Looks like he was humping her while she was asleep, then she woke up and he's like: "Oh shit, she noticed!", while Fluttershy defenitely finds the situation awkward, not knowing what to do now. Maybe she will commit her love for the little fluffy bunny and both will have a happy ending, in every meaning.
Well if Applejack for example finds out that you're also dating Fluttershy she wouldn't be too happy would she now? I heard that after years of apple bucking her Bucky McGillycuddy and Kicks McGee can hit REALLY hard. Ouch.
But even worse faith awaits you if Fluttershy happen to find out you're cheating. I'm not going even to start describing how much pain and torment she can deliver via her Stare(tm)!