I, too, am hoping you MRI will show something helpful.
AS for Flexeril, there are other muscle relaxants available. I cannot take Flexeril at all. Please ask you doctor about a different muscle relaxant.
Magnesium is a great muscle relaxant; yet, may not be enough.
(Not magnesium oxide.)
Do be sure you have adequate calcium and magnesium intake.
See the magnesium threads in the PN forum if you have questions about magnesium intake.
As for feeling fed up and thinking of suicide, I am very sorry for your deep pain.

Many of us, if not all, have been there. Some of us revisit that place over and over again on our journeys. The pain, the limitations, the isolation, the humiliation, the frustration and even the fear... are often too much.
Please show deep compassion to yourself during the most challenging times. You deserve love and compassion.
The Survivors of Suicide forum is a good one here. I am a member there, too.
It's a little quiet there this week. Yet, please check in there anytime.
Please continue reaching out!
I hope today is a better day for you!
Warmly,
DejaVu