Inflammation in under arms with training, computer work...

I have in the past 2 years suffered from a strange form of inflammation in my arms. The area of the aching is hard to describe but is showing in the underarm, most of the time on the upper side of the arm.

The inflammation started 2 years ago, while I was doing barbell bench press. I stopped training for a couple of weeks and when it was gone I started again, stupid mistake. It started again and it now took 4 weeks for it to disappear and then I started weight lifting again and the same thing happened but with longer recovery time. Now the last time I felt it disappear was one year ago.

It's not a constant inflammation but it especially appears while doing computer work with mouse and keyboard or writing long text messages. It does not appear if I'm doing mountain biking, playing disc golf or other stuff, which I find kind of weird.
I have tried a lot of different things and approaches: wrist support, NSAID pills, chiropractor, physiotherapy, zone therapy, nerve conduction test and so on... Nothing helps discover the reason for my aching, sigh.

I'm really getting depressed by the symptom and not being able to live a normal life or working out.
If you have any suggestions for what I could do to get rid of my problem please tell me, I will be forever grateful!

If you have any questions for me please ask :)

Kind regards,
Rasmus
Denmark