Hello and welcome!
I am not a Doctor so please forgive me if I miss something or misunderstand, but I will try to share with you what I know and what I experienced myself. Hopefully will help you.
Personally, what you explained relates to your muscle issues. Exactly the same symptoms I and many other experience when they either sit in front of computer too long, or do some house work or gardening or exercise or some other activities which they don't do every day of their lives.
Sometimes even sleeping wrong can cause same symptoms only b/s your muscles somehow get inflamed due to uncomfortable position in bed or due to using them more than usually, or even a bad weather day may cause some muscle pain. My son is only 27 very fit and in great shape but often he complains about same thing if he does something. The other day he went with his gf to NYC and stocked in such bad traffic. He spend 4 hr behind the will and came home complaining of tingling, pain, burning sensations. His back was hurting him and when i tried to massage his back, I felt lumps of swollen muscles under my hands.
Would you believe that simple stress day by day can leave our muscles very tight around neck and back areas causing so much pain, inflammation of the muscles, and other symptoms you described? Yoga, relaxation technics, meditation - if you learn at least one of them, you will feel so much better!!!
I am very familiar with all this so it wasn't something I was worry about, but for someone like you, to whom these type problem is new, it can be frighting, I get it.
I would suggest you to stretch every single day; try slowly and gentle and add more minutes every day. Couple times a day - ideal. Of course build your muscles gentle in the beginning; this is the best advice I can give since "been there - done that". Swimming, walking in swimming pool, body massage, relaxation, meditation, yoga - I promise you, you will feel 100% better!
I dont know how old you are, but since we 25, our spine start to change and usually by age 40 we can see some changes on x-rays and MRI, CT scans. If your DR doesn't see anything on yours - you one lucky person. So it means you should try all the above healthy stuff to improve your muscle health and you will see a big difference. You will see it soon after you start.
Luckily not every symptom, not every pain is a disease. Sometimes solutions are easy and right here, we just have to try them all to get better.
And if you try it all, like they say, but your symptoms get more serious and worsen, you have to go and do more extensive search with blood work, etc.
Best of luck to you