I don't think your pain is psychosomatic. I think you have inflammation and some sort of reaction to the injury, that will take time to heal.

I know for myself, I have various times at night when my feet hurt and then don't. I can get up in the night to use the bathroom and my feet do not hurt then. They most often hurt/burn when I lie down for sleep. It seems they are on a clock.

Also some foods tend to make the burning worse for me. This is an individual thing. But my triggers are monosodium glutamate found in foods, (called MSG) and also potatoes. (that sounds odd, but it is true-- I get burning from them if I have them that day) . It took me a LONG time to find the food connection.

Some things I discovered, helped my feet quite a bit. One was dextromethorphan found in cough products. I had a terrible bronchitis last Feb and took quite a bit of cough medicine, and the DM was very effective for my feet. This may not work for everyone, but DM is a NMDA pain receptor blocker, and MSG is a stimulant for that receptor. So by removing triggers and doing a mild block, I accomplished quite a bit and learned alot.

Filipe, you might want to keep a journal when your pain is worse, and when better. Include everything you put in your mouth and swallow that day. You may find some trigger of your own.

Some injuries take a long time to heal. Tendons especially. And the shoulder joints are very complex, and the shoulder blade is kept in place by fascia and tendons. So you might just have to wait longer.

Valium is a muscle relaxant, and also a mild antiseizure drug, and may be working that way for you. It is also very habit forming and symptoms can return with a vengeance when you stop using it. It will cloud the whole healing process.

If you can get ahold of Lidoderm patches, they would be worth trying. If they block the pain for you when applied over the shoulders along the back where the strain originates, it will tell you which nerves are affected. You can block the signals and eventually they will settle down. I had a nerve in my thigh damaged from a C-section that stopped finally shooting after 14 days of using the Lidoderms (which had just come out on the market). I still use them for my lower back if it flares up, and sometimes on my knees, which have arthritis.

I don't think anyone here can diagnose you. The term chronic neuropathic pain, means nerves that are diseased (pathology). You don't know if they are "diseased" or just sending signals out from an injury. All pain is sent in the body via nerves. All sensation is sent by nerves. And movement is mediated by nerve transmissions. I think it is probably more accurate to say you have chronic pain of unknown origin at this time.