Thanks for the more complete story, Filipe.

So...this is how doctor's narrow down triggers.
In your case, you were fine before the strain at the gym with the dumbells? Then you were a bit better, until the massage?
This says to me you might have some "strain" which is going to take time to resolve and get better.

Is this accurate? What this says, is that something triggered your symptoms. They didn't come by themselves. People with chronic illness, typically don't have a big trigger like this.

I had a massage years ago on my back, --I went with a friend -- and the masseuse triggered my shingles in my neck (which I had a couple of years before)....I had 3 days of pain, which slowly resolved.

I would use cold packs on your back and neck daily. I'd get enough rest and not strain yourself further. Eat healthy foods, avoid alcohol in excess and try to relax. If you get worried, and anxious, it will make pain worse. This happens for everyone.

There are patches you can get for your back. Some are RX only like Lidoderm. (these are numbing agents) I don't know if you have those in your country.

Others like Salonpas are international in many countries.
They can reduce inflammation and take the pressure off the nerves. ( I did some Googling and Salonpas are in Portugal).
http://www.salonpas.us/salonpas.php

I use these alot for my pain flares and they work for me.
You would apply them to your back where you think you strained yourself. neck or upper torso.

Sometimes an injury takes a while to heal up. Sometimes it needs help too. I'd take some fish oil too to reduce the inflammation and see it that helps.