Lower back pain?

OKAY SO@! I was working with a physical therapist a while ago for things completely unrelated to my back, but he discovered that my vertebrae were immobile and thus reducing my lung capacity / range of motion / etc. SO i was working on it 3-4x per week and it was getting a lot better. I no longer woke up with lung / rib pain, my lung capacity about doubled, and i was feeling a LOT better. NOW i've been busy and he's been in the bahamas, so we haven't worked for a couple weeks. my lower back is killing me to the point where i cant sit / stand still without shooting pains. does anyone know of any stretches, etc that i can do on my own to keep my back the way it was?? plz? care-utz?