There is one more factor I'd like to mention:

If you have used in the past a drug from the fluoroquinolone family (Cipro, Levaquin or Avelox)...you need to know that these drugs which are common antibiotics and used for UTIs and pneumonias, can affect the tendons and cause ruptures and other pathology. Somehow they interfere with tendon maintenance. This usually happens AFTER the treatments and is often overlooked by doctors. The toxicity of these drugs is considerable.

This may be a factor for you in addition to extreme physical activity that also stresses tendons.

Tendon injury takes a long time to heal. It might be a good idea to see a hand specialist at this point.

Thanks for information, MrsD,
in fact I did use cipro for UTI, but it was in December 2016, so about 6 months ago. After just few doses my left arm started to shake and give up when i was working out so I found horrible stuff about cipro and requested another antibiotic (which I got).
NOw I am not sure how much damage can 3 or 4 days of cipro can do, and how long effects can last, but after what I read, this medication should not be given to someone who exercises or plans to exercise. Also, you should never ever take NSAIDs (any) during or soon after you are finished with cipro.

Unfortunately the tendon damage I believe goes on for months and even years. These drugs damage DNA...and somehow affect tendon maintenance which may be permanent. I sure hope not.

This effect because of the long delay in onset was first discovered by doctors who used the samples willy nilly on themselves and their families and subsequently later much after the infection was over, ruptured knee tendons and achillies tendons! We had a poster here in the past who ruptured a biceps tendon moving furniture. I have yet to see any research about this explaining how it works, but the fact remains that the tendon damage remains a LONG time after the drug is stopped.

Your age and gender are against you now... lowering estrogen affects many things for women. Also if you have been pregnant in the past, you join women whose tendons change after pregnancy. During pregnancy, the body makes a hormone called relaxin to help the pelvis dilate during delivery. It relaxes ALL tendons and it can weaken some in those with a tendency to have connective tissue problems. Women notice their feet get bigger after pregnancies and this is one obvious sign that relaxin has loosened their feet which are held together by ligaments/tendons. In your case you might have additive triggers for your problems today.

A hand specialist may have a treatment or surgery to help you. At least a hand doctor can give you a support or a brace of some type to immobilize your hand to enable faster healing.

I read that too about cipro. Also, my arm tendon was damaged long ago, so one push from this medication could have made it much worse. Of course, I was pregnant thou it was long time ago, but it could made some damage too.
Currently I am going to physiotherapy and I use hand brace, but I still have a lot of spasms, especially at night. I have to take some muscle relaxers to sleep, because it's waking me up.
My tendinosis is weird since it's not painful, well, almost not. But the spasms in hand are scary as hell, especially as I feared it's something neurological (i still hope it's not).

How about total rest of that area for an extended period?

So do the epsom salts before bedtime . The soaks are really
good for relaxing things before sleep.

I tried relaxing first, but it's hard since I am right handed and single mom who does everything. Pretty much I can't afford to rest my hand, I even tried but it seemed that made spasms much worse somehow. I think I tried too hard to make my hand "limp" so instead it was even more tense (because it wasn't natural but forced rest) and trying too hard to rest it makes twitches even more apparent and visible.
I will have to soak my legs too now since I am getting cramps in calves too.
What bothers me is that just 2-3 months ago I was in top shape. Now I feel like a wreck.

I find that taking corn syrup, corn starch and corn out of my diet reduces myoclonus jerks in my hands. Read labels carefully as things you wouldn’t expect like cough drops and probiotics have corn products in them.
Hope this helps you.
Jean