When your back goes "out" like that it is a sign that your inherent stabily is not sufficient. Old injuries to the ligaments and joints will cause this. I think that Limewave suggested Pilates, I would second that suggestion. Having the chiro correct your alignment is temporary solution. You body has to learn how to control the movement of your back and core/pilates exercises are the best way. Keep you with your stretches too. They're also really important.

Hope you're better soon.