Both pain & meds interfere with deep REM sleep, e g., Delta pattern brainwaves.
Try Hemp gel capsules omega 3-6-9.
Rx for melatonin, the go to sleep chemical, can be helpful. B-12 chewables early in the day causes melatonin to build up in the brainstem's sleep center by day's end.
Valerian Root supplement is touted to promote deep, restorative sleep, but some people don't seem to tolerate it.
White noise (soundwave machine or air filter) or foam ear plugs (to reduce or block background noise), complete darkness (eye mask), cool mist humidifier, & if rx'd - faithful use of one's CPAP or APAP machine are all part of a total sleep hygiene routine.

Just speak to your GP, they will know what you can take with your other meds, everyone reacts differently.
https://www.spine-health.com/treatment/pain-med...

A lot of the ones mentioned here aren't even muscle relaxants, Gabapentin for one which is for nerve pain. I was prescribed Baclofen when I had severe whiplash and it did help, without any side effects, but, as I said, everyone is different and reacts differently to meds. The only person who can say what might work for you, is your GP. Go see them and ask what they can give you to help you sleep, without side effects.

I have been taking hemp cbd oil when I feel this way. It seems to help relax me so I can sleep.

I took everything your needing something for pain. Go to a Rhematologist. Or pain specialist. Please just don't go that route. Get those Dr. Then if you. Don't get any relieve. Pray. Read your bible.pray it's so hard but these drugs hide the real reason. If nothing else get 180%whisky JACK DANIELS. Fill a cup with1/4 whiskey,1 large squirt lemon, teaspoon honey.and a real hot boiling water mix and sip till all gone.take 20 minutes before bed. Go to bathroom and everything before you start drinking your totty. BLESS YOU SWEETHEART.♥🙏🙏

Baclofen is a muscle relaxer I take. I use to take Flexeril