stretching quads

Hello, I am a 64-year old man who maintained very good conditioning and strength until about 16 months ago.
I sustained injuries behind my knees from knee wraps bunching up there during my squat exercises. Doctors only suggested pain medicine and stretching.
September of 2012 I went to a private massage therapist who injured my hip-flexors with her knee-raise and pushdown test. One week later she injured my quad muscles with her elbows pressing down into the muscles on two successive days producing next-day pain and stiffness which lasted for many months! Again doctors offered pain meds and stretching- to no avail.
I walked a little and streched my quads by putting my ankle or shin up on a chair arm, bending the leg at 90o- which is not as high as I could go- daily. But my pain only subsided after another 2 months of mostly rest.Now after 5 months of no pain and walking up and down hill ok, I was advised to hold that quad stretch for 1 minute instead of my usual 25-30 seconds. Right after I tried that my pains returned!
I backed off the stretching, and it again gets worse after modest activity and improves after a days rest.
What to do now after a moderate, lengthy sretch has caused pain?