Since I've been?

Yes.

Think it should be,"I have been trying to keep myself busy since I was off work". Is this wrong, GPY?

tenjing Think it should be,"I have been trying to keep myself busy since I was off work". Is this wrong, GPY?

It doesn't work very well.

CliveI' suggest I have been trying to keep myself busy since I stopped working / quit.

For me, "since I've been off work" and "since I stopped working / quit" mean two different things. "off work" is a temporary state, typically due to holiday or illness, but here probably implied to be the latter.

Idiomatically, I commonly people say . . . since I went on (longterm) disability

Is this what you mean by 'ill'?

CliveIdiomatically, I commonly people say . . . since I went on (longterm) disabilityIs this what you mean by 'ill'?

I just edited my reply slightly, as you will see, but as far as illness is concerned, I guess it could be that, but "off work" to me usually implies that you have some hope/prospect of returning. Long-term disability sounds more like a state ben

If it;s just short-term eg the flu, I always say and hear simply eg He's off sick.

Off work is implied as a temporary state here.

Stopped working or quit changes the meaning altogether.