Hi AppleTree

A few suggestions to help find the cause of the problem:

I've read many people have a drop in blood sugar during the night which can cause them to wake. Having some form of protein (eg a hard boiled egg or some yoghurt etc) just before going to bed can help sustain the blood sugar level through the night.

Another cause of waking and not being able to get back to sleep may be low cortisol levels - have you had this tested?

Also disturbed sleep is frequent among those who have Fibromyalgia (and other conditions). It is cause by Alpha Waves interrupting the deep sleep cycle.
I don't understand it fully but if you search "alpha intrusion sleep disorder" you may come across some info that helps.

All the best finding solutions.