Damn you all! I just rewatched that confession in 2x20 and Barry's face was magnificent. His tone of voice was small and even shaky at times, like when he said "Why are you telling me this now?" (Credit to GG on that part). Iris took her time telling him how she felt, trying to be careful to not overwhelm him (That failed because he was already overwhelmed) and being very shy about it. Even the way she sad if he still wants a future with her, she was like a love struck teenager.
Both of them were so amazing in that part; it’s my favorite WA scene of the season. Both of them are so good at adding so much more to a scene without so many words, especially in that scene but focusing on GG right now. Barry has those moments when he looks at Iris and see that something is wrong, we saw it in 2x09 and 2x17 and he did it again in that scene with that little “what’s up?” and that small grin and his head cocks to the side, but he lowered his voice just a bit. And then she starts talking and at first there’s confusion then she says “you’ve always had someone to come home to, me.” and he’s bewildered and frozen in his place.
And Iris continues talking, saying “I’ve been thinking about us.” He’s still nervous and there’s that tiny part of him thinking “oh no what is she going to say?” and thinking “I don’t want to be hurt again.” Then she says the words that he’s always wanted to hear, but at this point never thought he actually would. His eyebrows shoot up, the suspicion in his face disappears, and his eyes soften.
And he’s just trying to process the whole thing, he looks away for a second, overwhelmed and really really shocked, then he does that thing where he touches his lips probably for a split second thinking about the 1x15 kiss and the stammering “When I told you how I felt about you last year?” There was the tiniest quiver in his voice. And he’s rubbing the back of his neck just trying to figure out what to say next, but he put that nod in there because he was really listening to what she had to say and he wrings his hands together when they both step forward because he wants so badly to just accept this moment, and hold onto her but he can’t, he’s terrified of the other factors surrounding him at the moment, the particle accelerator being the main one. So he tears up because he’s thinking “finally.” But he’s also got these barriers in front of himself and protecting his heart after being hurt so bad last year so he does the only thing he can think to do which is let her walk away.