Interesting you had shingles recently. that indicates a low immunity and you issue might be nothing more than that. i.e. Your body is not healing normally at present and needs time to get itself sorted. if you aren't getting anywhere with a Wikipedia reference-linktennis elbow approach one might propose that you don't have tennis elbow. What do you feel is the specific thing you did that has brought on this issue. You mention shoulder rehab. This may be a neurologically referred pain.