Tight left hip, glute muscles causing left lower back pain

My left lower back hurts the next day after walking or peddling a bike- from something in my left hip or glutes. Hard to pinpoint the source as the whole area gets tight. The outer thin muscles are tight but I think its from very deep inside, as I can loosen the outer but its still tight very deep. Its not sharp, but very achy and tight, limits motion. Gets better if I stop taking walks or bike rides for 1 week, but comes back as soon as I resume mobile exercise.

I hear runners get this sometimes? Anyone have some advice?

I used to be very fit and am familiar with most stretching. I have used myfacial muscle tension release (AKA Trigger point therapy) on myself with the Thera Cane and various tennis and golf balls- on the floor.

I've searched all muscles for the point of pain origin, cant find it! I went farther too - quads, upper back, checked out the right side in case it was really referred pain from the right side.

I had this on the right side years ago- it just went away.

I do have hypothyroidism and that does mess with muscle / tendon recovery even if your treated properly some times (thyroid hormone replacement per Free T3 and Free T4 testing.)

[LazyMoose]

Went to chiro, left side of pelvis was out of place, SI joint fine. Feel better.

Wish I could 'crack' myself!