Lupus Vs Fibromyalgia

How do rheumatologists tell the difference between pain caused by Lupus (or another connective tissue disease) and that of Fibromyalgia?

My inflammatory markers are never raised, despite other tests confirming there is inflammation, so I'm curious if there are other ways to tell.

I was misdiagnosed with Fibromyalgia a couple of years ago, either due to a poor rheumatologist and/or someone else's referral being accidently mixed into my notes (they had Fibromyalgia). I'm scared to contact my rheumatologist about current issues for fear of investigations/treatment going backwards, but I am aware they can co-occur, though. I also don't want to bother them if it's not necessary.