Yes I have hypermobility and a bad si joint.
Pilates is your friend! Gentle clocks at bed time, leg raises while holding tummy in. Ideally look up best positions on YouTube and go to a class.
A good physio will check alignment and adjust and give a similar Pilates set of exercises to do. But also assess what it is in case something else.
I find rolling on a spiky rubber ball helps, especially around bottom, but it’s definitely all si joint / posture related in me.