You are describing my pain to the T!
Through MRI I have discovered the cause is a herniated disc at L5 S1, and a bulged disc at L4 L5.
I have been dealing with pain in my left glute for a year. I also have pain down the back of the leg to the knee. Then it jumps to my ankle/calf.
Back in the Fall I had a series of cortisone shots. They took the pain away. But as soon as I returned to working out, the pain returned.
I now avoid anything that bends the body forward. It sucks.
I am at my worst upon waking. As long as I stay upright and moving, it is tolerable. Being sedentary is the worst for me.
I don't have any miracle cure for you. But I highly recommend listening to your body. If you can afford it, I would get an MRI.
I feel your pain.