I had a lot of lower back pain and it was muscular fatigue on the exterior side of my lower curve. It was due to compensation from my upper curve.
Can you get in to see an ortho? In the meantime, you may want to get xrays done, and see a physical therapist to learn how to strengthen muscles in other areas of your back to offset the stress on the area that is painful. That helped me for over a year. Ultimately I ended up getting (first time) surgery 6 weeks ago, because apparently my spine was collapsing in on itself like a black hole.
Best of luck, and yes, yoga will also help. Any stretching and strengthening is good, but again, a PT will help you identify and isolate the best exercises and areas to target.
Good luck.
Female, age 38
4 years of bracing, concluded at 42*upper/38*lower
currently 64*upper/40*lower
Fused T3-L4 on Feb 23 2011
now 32*upper/18* lower