I am not looking for a specific fic, but I have been dying to read a story with this plot and was wondering if it might be out there (or something similar)?
So, longer explanation: Tony and Virgin!Steve start sleeping together and have a friends-with-benefits relationship (Tony wanting to introduce Steve to the awesomeness that is sexy times with other men). They continue sleeping together for a couple of months. Steve, being Steve, is respectful to his sexual partner by staying the night in his bed, bringing breakfast in bed, etc., which Tony interprets as their FWB relationship developing into a legitimate, committed relationship. Tony, being Tony, of course doesn't communicate this because to him (and the team), it seems that they have fallen into a relationship and finds himself pretty deliriously happy with it.
Unbeknownst to him, Steve, completely oblivious to all of this and still thinking that they are just FWB who are seeing other people, begins dating someone (Sharon?). As it gets serious, he tells Tony that they can no longer sleep together because he's finally met someone he thinks he can settle down with (either because its a woman or he doesn't see Tony as a long-term relationship). Cue complications and such.
So, short prompt: Tony and Steve sleep together. Tony thinks they're in a relationship and Steve doesn't. Steve starts seeing someone else.
I don't mind if its a happy or an unhappy ending. I would really prefer if Tony and Steve didn't end up in a threesome relationship with this other individual. Also, I would love it if Steve wasn't intentionally being a dick.