Has anyone ever heard of adult onset autoimmune distruction of the parathyroids

Almost 5 years ago I had a total thyroidectomy d/t cancer. Anyway....4 yrs. into post surgery,(I really say 6mo.) after surgery things started going haywire with me. To make a long story short...I've been experiencing muscle spasms and muscle movement in the trunk of my body along with my calves in the begining. Now almost 4 yrs into it, more symptoms have popped up such as intermittent pins & needles  at the bottom of my feet when I walk. (I can't even ride a 4 wheeler without my legs feeling like they're vibrating.) My right arm between the wrist & elbow twitch as well which makes my ring finger twitch as well. My eyes at times hurt so bad as well. (the eyeball it self) My pcp drew blood and found that my PTH is at 4 however...all other blood work such as ionized cal. 1.22 mmol/l, vitamin d 1-25 is 46 mag. normal along with phos. again normal. Last year they did a blood draw to see if this was any type of autoimmune disorder and every thing came back normal.  They even checked my cortisol which came back normal. All I know is when I start with the spasms their quite hurendous!  My TSH is 0.54, Free T4 1.37, and Free T3 2.72 which they say are all normal. My question is?
What makes the pth low?
Can a person have adult onset of distruction of the PTH and if so, what happens when it goes to 0?
Other possibilities I have thought of are Fibro however I don't have the trigger points
The other possibility is MS, did some reading on this as well and both MS & Fibro have alot in common other than the distruction of the myelin sheath.
My Endo suggested I have an MRI done. What do you think?
I'll be seeing my pcp next week to try and get some answers and maybe some sort of referral
All possibilities welcomed