Account compromised

I'm emailing here accessed via my son's account, as cannot access my personal Microsoft account. When I try to log in, a completely unknown email address showing as fi*****@uberip.com comes up for any confirmation codes to be sent to. I've tried the official account recovery route too, and even though I clearly marked the address of the account I'm trying to recover, although the email notification came through to the correct alternative email address I'd given it, the notification linked my account to another spurious email address, this time (fi**@outlook.com). again an address that is absolutely not one that I have ever held, made or used.