A cyst maybe? Do you have a slight fever? Is your back warm to the touch in a very centralized location? Do you feel a lump/bump under your skin?
Not enough water? Kidneys maybe?
Bulging disc causing sciatica? Odd sensation going down and around your thigh? Is your big toe numb?
All of this of provided its not just a simple strain or pull.
I don't think more protein is the answer.
i dont know if its a buldging disk seems that it does stick out on each side of the lower spine where it hurts near the glutes when i press in but maybe thats normal bone or pelvic by the spin
i dont get any sensations going down to the thigh but if i were to do a medium height kick i would feel a pull in my lower back
i drink tons of water i doubt this is the case. im not even that over weight for my height