sore and tight glutes for 5 months, unable to sit or resume normal activities

I have been sore right around both of my gluteus Maximus muscles since December.  The muscle is very tight and seems to be restricting the movement of my lower lumbar.  It's uncomfortable to sit even for short periods of time as there is a dull pain from my glutes down the back of my legs.  I have been to a spinal PT and I temporarily felt better but not much.  He focused only on my spine and said my movement was very limited for a 27 year old.  I had an X-ray taken in December that my Internal Med. Physician initially said revealed dehydrated discs around the S1 area but later said they looked fine.  I have been doing yoga 3-5 times a week the past 1.5 months and been to a stretch therapist 5-6 times the past three weeks but the problem persists.

Background:
I worked out a lot - Crossfit 5-6 times a week + a little running - and wasn't great about stretching.  My hip flexibility was not good and I was sore all the time.  I have also been studying a lot - 10 hours a day - and my stress level from November through February was higher than normal.

I am just wondering what I should do about my situation? I want to be healthy again and resume my normal lifestyle.  

[Michael L Gross, MD]

You mention running. Running on a treadmill is different from running outside, and often can lead to hamsting tightness and spasm. I would suggest a program of hamstring stretching, as well as hip flexor stretching and strengthening. This should be combined with exercises to build core strength and balance.
On the stress side, relaxation is very important. Consider relaxation techniques such as meditation. reiki, acupuncture, and massage therapy.

[Kevnm67]

Thanks for the suggestions Dr. Gross, I appreciate your response.  I have been working on increasing my flexibility very consistently but it hasn't helped.  My core strength is pretty good and it was a consistent part of my workout routine, but what exercises do you suggest?  And which hip flexor stretches would you recommend?  

Also, I forgot to include that studying meant I was sitting in a chair all day and a lot of the time I was leaning forward with my back hunched.