Bucky/Tony fic - Winter soldier split personality, Bucky doesn't know
Looking for a fic where Bucky is with Steve, but needs Tony to maintain his arm. Bucky is so anxious about it, that without him realising, the Winter Soldier takes over. Winter and Tony start an affair. Eventually, Bucky realises he is missing time and intentionally stays aware for his appointment with Tony. He also ends up sleeping with Tony! Winter is not happy! And at this point, Tony realises there are two distinct personalities. Bucky becomes aware of Winter, ends up splitting with Steve (who is very controlling — not a nice Steve fic). Steve triumphantly tells Tony he has been sleeping with his parents' murderer, hoping to destroy their relationship, but Tony already knows. Tony, Winter (who changes his name to something else...?) and Bucky end up happily co-existing.
I don't know why I can't find this fic, as I've read it several times!
Update: Found it. It's Under Pressure (https://archiveofourown.org/bookmarks/628057143)