Its always hard to isolate the grip problem from the rest of your position. Maybe you should analyse your whole riding position, from pedals, to saddle, to bars, ensuring that your back is straight at an angle you prefer, your shoulders and elbows are relaxed, your wrist is in a neutral set, and you hands are supporting weight through the palm, not the edge.
In the meantime, cut back on your riding before you do any more damage.
If you can find a good professional bike fitting service it may help, but many will simply get you into the right ballpark for an averagely-dimensioned person.

Check out
http://www.peterwhitecycles.com/fitting.htm