I went through similar issues last year. Mine was "Golfers Elbow" rather than tennis - which was directly related to squeezing the racket handle too tight.
Also switched to a softer racket (Babo Pure Storm) and away from poly strings to a multi mix. So far favorite is Wilson NXT Control, with Babo Addiction coming in second. That allowed me to keep the tension where I prefer (57-9), but soften up the string bed.