@Domido – Hey there! It sure sounds like you’ve got an uncomfortable situation on your hands - or armpits, as it were.
I, too, get razor burn under my arms when I shave, but it sounds like this might be a little more than that. It might be best if you pop into your doctor’s office just to get that rash in your armpits checked out.
After all, it might be that there is a simple solution to your problem. Then you could be symptom free and still have nicely shaven armpits!