The part of the sentence "I was mentioning" is grammatically correct and can be used in written English. You can use it in many different contexts. For example: "I was mentioning earlier that I'm not sure what to do next.".
7.48pm: So I was mentioning the nineties, yeah?
I was mentioning somebody, and she didn't think they were "edgy".
One is a sort of anticipatory quibble: the real problem here is that, as I was mentioning before, something is really wrong in both the state and the local infrastructure and in the Department of Homeland Security.
Until one time we were talking and I was mentioning an idea for movie and he said "I don't know, it doesn't feel right for me" and we began talking about baseball, because he's a big baseball fan, and I'm also quite a fan.
Oh did I mention it's fast.
As I mentioned, Obama was my guy.
CRUZ: If I could just interject, since I was mentioned.
I love the desktop app, it’s always running on my Mac. Ludwig is the best English buddy, it answers my 100 queries per day and stays cool.
Cristina Valenza
Retail Lead Linguist @ Apple Inc.