Two words... "Natural Gut"
I used to hit with a stiff light weight racquet with old nylon and/or poly for 30-45 min at a time and my elbow hurt so bad I could barely put it on the steering wheel to drive home. After giving proper time off to heal and switching to natural gut (even in a Bab PD strung at 62#) plus a vibration dampner I have no issues at all.
A friend who is a PT with a PHd says some cases of TE can take 6 months (of no tennis) to heal.
Hope you feel better soon!