noah123

Have you tried heavy weight lifting? Light weight lifting and yoga won't really make your muscles that much stronger. In order to get stronger you have to consistently add weight to the bar. I know alot of women are afraid of getting bulky, but unless your are dieting specifically to gain muscle it will not happen.

To build up your back I would recommend learning how to deadlift properly, and then just doing one set of deadlifts for 5 reps, once a week, adding weight each week. If your back still hurts when you can deadlift 200 pounds for 5 reps, with good form, then you'll know that weight lifting isn't going to help.

That might seem like a ridiculous amount of weight to you, but I trained my girlfriend to the point that she was deadlifting 260 pounds for 5 reps in less than a year, and she still maintained an attractive feminine figure. There is a girl, at the gym I go to, who can deadlift 325 or more pounds for a single rep, and she weighs something like 105 pounds, so she isn't bulky or big at all. She has a very nice figure in my opinion.

It would definitely take some hard work and commitment to get to a level of strength close to that, but it might really pay off for you.