Lower back discomfort/upper buttocks discomfort when sitting

Yes. Pain like this is usually from the discs. I would say your lower back is out of alignment.
1) You do not have a natural inward curve to your lower back when you sit.
2) Your spine has shifted to one side.

Yes, try this to put a curve in your lower back when sitting:

1) "Static extension on elbows" (Do a Google search)
- To get your shoulders pulled back as well, pinch your shoulders together.

2) "SEATED ABDUCTOR PRESS" Part I
a) Sit at the edge of a low step so your thighs are parallel to the ground.
b) Wrap a belt or Yoga strap around your thighs just ABOVE your knees.
c) Press outwards against the strap for 2 seconds. Repeat 20 times.
- As you press outwards, let your hips rotate forwards, putting an arch into your lower back.
- Do NOT let your feet roll in. Keep weight on the outer edges of your feet and off the balls of your feet.

if that does not help:
Engage your inner thigh muscles with the
3) "SEATED PILLOW SQUEEZE E-CISE" (Do a Google search)


If your spine is shifted to one side, try these:

1) HAND LEG OPPOSITE GLIDES:
a) Lie face down on the floor with arms extended straight overhead.
b) Let your ankles drop out to the sides so your feet are pigeon-toed.
c) Reach UP with the LEFT ARM and DOWN with the RIGHT LEG.
d) Now switch and reach UP with the RIGHT ARM and DOWN with the LEFT LEG.

2) "STANDING WINDMILL" (Do a Google search)
a) First shift your torso to the side, THEN bend to that side.
b) Bend left / right with your feet at 3 different widths: shoulder width -then wider -then wider still.
c) make sure you bend just as far to the right as to the left.

3) "YOGA TRIANGLE POSE" (Do a Google search)
- Against the wall, NOT free standing!
- Keep both hips at the wall - one may try to lift off the wall.