Steve might have been blushing, but he was no virgin by the time he got to Europe and rescued Bucky in Italy. He was a lamb among the wolves on his USO and war bond tours, a polite and decent innocent among the voracious Hollywood actresses and aspiring showgirls and they took advantage because Steve got into trouble once the first polite refusal was ignored. (He always refused at first, because he’s a nice boy, but he never really felt bad about the inevitable conquering because while he’s a gentleman, he’s not a saint and he wants.) Golden Age Hollywood was no better behaved than current Hollywood, but they had studios and complicit media working to hide it better. Steve, built like he was and clearly not out to play bedroom bingo or likely to brag about it afterward, wasn’t a refreshing change — he was a challenge to be met.
Marlene Dietrich, who did yeoman’s work for the troops as a frontline entertainer, took numerous lovers throughout her career and probably ate Steve alive. And yes, Peggy absolutely reminds Steve of her, although he won’t tell Peggy this because he knows Peggy knows (about Marlene, absolutely, about the others, he kind of suspects but certainly isn’t going to ask). Dietrich wasn't the only one, although Steve was never really promiscuous by anyone's metric, and he remembers almost all of them fondly.
[He reluctantly tells Bucky, who presses until Steve spills. Bucky listens with a mixture of slack-jawed awe and glee and pride. And envy, but he can’t really begrudge Steve for making up for lost time with Marlene Dietrich, even if she had to club him over the head and drag him back to her hotel. That part, Bucky is totally unsurprised by.]
Peggy expects him to have learned something from his experiences, at least with respect to dealing with women who are attracted to him, but he hasn’t, not really. He’s got no radar for subtle signals and he’s never made the first move and it takes Peggy a while to realize this. And even longer be charmed by what it means instead of frustrated and irritated and not a little hurt. He is still the man she met at Camp Lehigh, still waiting for the right partner, and she regrets, after his crash, that it took her so long to realize it.