Burning Pain in Hip Flexor

I have a burning pain in my right hip flexor area right where my thigh meets my pelvis. It only affects me at night lying in bed. The pain isn’t in the joint but in the muscle. PVC rolling alleviates it but only temporarily. The burning feels like rotator cuff burning, if you have ever had that. I am stymied by what is causing this. I have been stretching and doing mobility work religiously.

Could you upload an anatomy picture of the pelvis with an the area circled? That could help us give you an idea.