I would say that you have wrist flexor tendinopathy. The reason i think this is because of the nature with which you get the pain eg. when doing exercises involving wrist flexion (bicep curls) and wrist stabilization eg. doing weights, using work tools etc. To test whether it is this, the location of the pain would be on the medial (inner) aspect of the forearm and elbow, and stretching the wrist and fingers back with a straight (extended) elbow. The problem seems to be getting worse (the pain working its way down the forearm) because you keep doing the activities that irritate the tendons, now i am not saying you should stop working, but maybe you should try and limit the activities that stress the wrist and elbow eg. lay off the weights for a while and just focus on stretching the wrist and a light eccentric strengthening program. There are lots of