Hi there
Welcome to the Forum. Have you had that severe abdomen pain checked out? It could be unrelated to your other symptoms. Gallstones might be a possibility and it would be worth your while asking if you can get an ultrasound done to check. I mention it because I had severe abdomen pain in and around the same time as many of my other symtoms started. It was a while before my GP got round to sending me for a scan and lo and behold I had a heap of gallstones. I eventually got my gallbladder removed.
As far as your appointment with the Rheumy goes, make sure you write down as much as you can remember of a symptom list. Its all too easy to forget some things when we are flustered during an appointment. Be sure to mention your under-active thyroid as well. I also have hypothyroidism and it is relatively common in people with autoimmune problems but not exclusively so.
If you are in pain a lot, rank your pain levels on a scale from 1-10 so that you can get across to the Rheumy the level of pain you are experiencing. Also if you can get pictures of your rash when its present, that can be very useful. Start keeping a diary from today and note your symptoms between now and your appointment.
Usually at a first appointment they will also ask for a family medical history so maybe do some thinking about that now.
Do you have to get any blood tests before your first appointment? If not, dont expect too much from the appointment as the Rheumy will likely want to run some blood tests to see if anything is showing up. You will probably be given a follow up appointment but dont forget to ask about some symptom relief in the meantime.
If I think of anything else I will come back and post again. Im a bit tired at the moment

If we can be of any further help dont hesitate to ask
Best of luck and let us know how it went
Take care for now
Joan:rose: