Have you gone to a sports doctor to see what other imbalances you might have?
To relay a personal experience about an imbalance I just found out about:
I have a slight curve in my spine too. Back in June, I did something to my back (fatigue on heavy deadlifts followed by an active weekend running around with my kids on my shoulders) and have been trying to work around it. I finally went to a PT at the end of August and she did an overall eval on me and has been having me work on hip mobility and better stability in my spine. She also just sent me to a sports doctor who confirmed:
1) I have a slight sprain in my lower back.
2) My left leg is 1/4" shorter than my right (they confirmed this with x-rays, the only way to know for certain).
Because of the sprain, the effects of the leg discrepency are aggrevating things more. The glute medius is getting spasmed with extended standing / walking and this translates into a lower back pain. Working the knots out with a tennis ball is helping a lot too. The leg discrepency is probably partly responsible for the sprain too, since I was out of alignment lifting heavy weight (275 was heavy for me).
2 probably explains why even in the past, I would get pain from squatting too heavy. I could also feel, during deadlifting, my right side working harder, but didn't realize this was the cause. I'll be getting a heel lift for my shoes soon. Only downside is that I liked squatting and deadlifting barefoot, so now I'll have to look into a pair of flat shoes.