As a chiropractor, this is my jam! We diagnosis and treat this better than anyone else in the biz, blindfolded with 1 hand tied behind our back.
Sciatica is a general term used to describe pain, numbness, tingling or all the above into the glute and possibly down the leg. Sciatica is a descriptive word, but not a true diagnosis. The true diagnosis comes from a thorough history and physical exam. When pain that starts in the back and travels down into the glute, leg and especially if it crosses the knee, is probably not just a tight piriformis.
Sciatica can be either coming from the back or from the lateral rotators in the glute area with piriformis being the most common. Sciatica that starts in the glute area and travels to the back of the leg is typically referred to as piriformis syndrome. This is a pinched nerve at the sciatic nerve location.
Sciatica that starts initially as back pain then dissipates and turns into leg pain is referred to as radiculopathy. This is a pinched nerve in the lower back. There can be a few different reasons for radiculopathy which I won’t discuss here.
Treatment for both is different and treatment times will take longer especially with the latter cause. There are several relieving postures for both types that a professional can give you.
If you have been stretching your glutes without any relief to the pain, numbness or tingling in the leg, then the cause is likely higher up in the lower back. Assessment is key to diagnosis and diagnosis is key to treatment!