hums-happily:

What if Mycroft is Greg’s “wife”?
(Hear me out)
When Sherlock tells Greg his wife is cheating on him, and with who, it is a different code word. Like they set up a system a long time ago to do it, cause Myc can’t always share where he goes for work or what he’s doing and Greg worries constantly so Sherlock gives him hints.

“She’s cheating again”= Mycroft won’t be home when you get there tonight, he got pulled away on a mission.
“She’s cheating with the p.e. teacher”= He’s on the run, but alive.
“She won’t leave you, Lestrade, don’t be stupid.”= He’s okay and he loves you. Stop worrying. 
“She slept with the grocer on her way home”=He’ll be home for dinnertime.

All these coded messages so Greg doesn’t worry as much as he would with just radio silence.

All these coded messages, just to remind Greg that he is loved.