Wrist pain down the outside. Doctors don't know what it is. No swelling. Is sore for about 4-6 weeks then fine for another 3-4 weeks then sore again.

Not sure. I assume you mean the little finger side of your wrist. Pain on this side of wrist has many potential causes. Tendinitis is most likely cause, but ligament injuries can cause this as well. Try keeping track of what you are doing the few days before it hurts. Excessive exercise, sports, or typing and writing could all be contributing to your pain.
Sports med consult. The intermittent nature of your symptoms suggests that a structure (could be ligament, nerve, tendon, bone, or cartilage) is getting irritated. To make a diagnosis, the doctor needs to know if there is associated numbness or weakness. Also what activities you do that may cause it. A sports medicine doctor can thoroughly evaluate this.