This is going to sound real dumb. But it really sounds like tennis elbow and I have a suggestion. It's actually a subtle and specific resistance training exercise that may help. Get a big rubber band, the kind that they use at grocery stores to bundle brocolli is perfect. Then extend your fingers and thumb together. Place the rubber band over your fingers and thumb and stretch the rubber band apart. Repeat in sets of 8-12 whenever you think of it.

This has had a very positive effect on my "lateral anterior tendinitis".