@dougs72 From what you are saying here that you need to sit and lean forward to be out of pain, that tells me that your hip flexors are probably very very tight. That will put pressure on your spine and pelvis. Sitting all the time causes hip flexors to be tight aggravating the problem because you need to stand and be able to move your leg backward to take a step forward with any length of stride. Your walking stride is probably very short. You may want to ask your physical therapist or doctor about this.

It will hurt a bit to press on the hip flexors to relieve the tension in them. My PT has used her elbow to press on mine when I'm on my back or I can lay on a small ball placed right inside of the Illium (pelvis) hip bone. I can also do this standing with a ball against the wall and lean on it with pressure. I think MFR would really help you, but you'll need to release the hip flexors before you can really benefit. You have to keep moving correctly or your body gets tight and stuck. I have to do this too or I will get back pain and my pelvis out of alignment. What helps me maintain strength and alignment is everything I do in owning a horse and trail riding. It's hard work to groom a horse, lift the saddle on and off his back, and I ride with good posture, and just a walking will strengthen my core muscles as I compensate for the horse walking. There are many therapeutic riding centers that offer this type of physical therapy.

I think what you are describing with pain that comes later is what happens when you overwork or overstretch something. That tells me that you do not move that much. That is fascial pain because it is stuck and dehydrated. You might not be drinking enough water which you need to flush out the waste products from living. The fascia is that cobweb like stuff that binds everything together. You have seen this before if you have removed skin from a raw chicken. It becomes somewhat liquid and reshapes itself with movement. Injuries, scar tissue, inflammation and being sedentary will kind of "cement" the fascia in place and prevent it from moving which is where you are right now. The fascia is important for transporting body fluids that help clear out waste products of metabolism and it weaves through and holds every muscle together and is an interconnected web throughout your entire body. MFR fascial therapy is for the most part not painful because it is very gentle massage and the PT waits for the fascia to unwind itself. You may experience some soreness when it first is worked on because it sounds like everything is stuck together. It will be the therapist pushing with "hands on" doing the work while you lay on a table. This cannot be solved in a day, and will take repeated sessions to work through and loosen all the layers of stuck fascia. Here is a video of living fascia so you can see how it is supposed to move. You can skip around, but probably want to look at the second half after they have talked about how they set this up.

There is a provider search at http://mfrtherapists.com/ and our discussion about MFR therapy:
Neuropathy - "Myofascial Release Therapy (MFR) for treating compression and pain"
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/
You may want to find an MFR provider and call them up and discuss your situation. They can tell you more about how they can help. When you had physical therapy before, what was the therapist having you do that wasn't helping?