Both of those. So much!

Oh, or, instead of Steve being suspicious that something strange is going on he’d be totally oblivious. Because hey, he doesn’t have a whole lot of experience when it comes to sex, since we all know he was a virgin before he and Bucky first did the deed. He mortifyingly confessed to this on that occasion. Of course Bucky forgot all about it afterwards, but Steve just thinks he’s being polite by not bringing it up.