Suspected trapped piriformis (not sciatica) - 'popping' gives relief

Hi, I really hoping someone can help me, as after two uncomfortable years of slow progress, I feel I am almost there, but am seemingly becoming more frustrated the closer I get.

My discomfort is in my lower left back - aching, and in my left buttock - niggling. It feels like something is trapped and just wants releasing. At one time I thought the problem was in my hip and stumbled across a hip joint mobilization technique that, when I attempt it, causes that 'yearning for release' feeling to intensify and sometimes, if I'm lucky, I get a popping, snapping feeling, which feels like the release I'm looking for, and the discomfort immediately eases. I presume this is something like my piriformis stretching over a bone or something else that is blocking it, before snapping into its proper position.

This new-found comfort can last between hours and days, but it always feels fragile and capable of getting back out of position at any time - by over-reaching, climbing steep uneven surfaces etc. Sometimes I will feel it 'pop' or 'click' back into the uncomfortable state, other times it must do it in my sleep, but I just can't seem to get it to stay in the right place. Afraid I can’t insert the link because the forum rules don’t allow it for new users, but if you google drbackman and hip joint mobilization stretch you will see what I mean - getting on all fours, opening the knees out and pushing back onto my hips.

Before 2 years ago I had no history of any such problems. It started quite innocuously, at the kick off to a football match (having already gone through a warm-up), as I pushed off to run something clicked in the left-lumbar region of my back and something immediately seized and inhibited my running in my buttock. Despite this I played the whole game carrying the injury, and after resting it for a few days and it feeling I assumed it was just a muscle strain. But the problem re-occurred the next time I tried running. I then stopped playing football but sought no treatment (not much cash for you expensive physios) for 5 months, over which time I got increasingly uncomfortable in my back, reaching with my arms became difficult and sitting was uncomfortable. Feeling twisted and pulled out of shape I approached a chiropractor, speculating that I had twisted my pelvis. The chiro concurred and applied some manipulation, and scans since suggest that my pelvis is now as it should be.

I have since had some NHS physio treatment, but that focussed on reactivating lazy muscles on the right-hand side of my back and didn’t seem to be getting to the nub of the matter, which is this feeling of something being trapped and pulling.

I speculate that it is my piriformis because I feel it pull when I open my legs out for things like a seated groin stretch. After I have managed to temporarily release it this pulling is not there.

If someone can help me understand just what is wrong and what I might be able to do to put it right I would be so, so grateful as it would put 2 years of misery and inactivity to an end.

Thank you for reading.
Additional Comment I forgot:
The reason I say it is not sciatica is because I'm not getting any symptoms in my legs.