It already exists: Google.
You might do your study, blood tests, what ever it is you want to have done. If the test says you are low on potassium, google "What food is high in potassium" and eureka! You need to add some salmon, potatoes, and a banana to your diet this week.
And then test yourself again a week or a month later.
Hopefully you find some way to test yourself that is economical (I was able to find a dozen at-home tests where you order a kit, some did cost a lot), but if you are in pain as you say, then go to a real doctor, describe your issues and ask for a full work-up. I'm sorry that you don't trust your local doctors, but google can help you find someone that has good reviews, or perhaps locate a trusted family doctor.
But just googling RSI (Repetitive strain Injury) indicates that nutrition is not enough. You need to be doing corrective exercises, strengthen your core muscles, practice better posture, and if possible change the type of motion that is causing the stress. Perhaps request a physical therapist who specializes in RSI to guarantee you are doing the correct exercises.
Youtube is also your friend.
- If we are specifically focused on the wrists, then do these stretches, stick with it for a week at least. Don't over do them, but do them two or three times a day.
I am not "Telling you what to do". This is what I found after about 10 minutes of google-browsing. I am not a Doctor. I am showing you two tools that not only cost billions of dollars to develop, but are completely free to use and can help to solve your problem.