Hiya G!
I'm having exactly the same problem, started about 3 months ago! I've seen the docs, chiropractor, a bowen practitioner, a physio and an osteopath (cost me a fortune!)
The advice I got from the osteopath has helped the most and 2 weeks later I can feel the difference.
This is what she told me, but it might be worth seeing one yourself. As nail techs we spend most of our time with our elbows bent and then on top of that time on pc etc. What can happen is the muscles in the biceps can shorten which pulls us forward, then the pecs shorten and means our posture is all wrong. She gave me some exercises to stretch out those muscles. The physio also gave me some neck exercises whereby you push your chin in with your finger, really hard to describe, lol! Also the osteopath recommended a quarter teaspoon of turmeric each day for 5 days then every third day after that. Apparently it helps release the build up of lactic acid that builds up in tense muscles.
Give me a bell if you want me to try n explain the exercises better!
Hope you get sorted soon, I know how miserable it is!