What next??

A few weeks ago my knee started giving me trouble again so I backed down on my cardio and didn't push it so hard anymore. Last week I got sick so I didn't work out much at all. So Monday comes and I was feeling good so I did a pilates video then rode my bike for 30 minutes. But as the day wore on my lower back started to hurt, and it kept getting worse. I was in a pretty bad car accident about 7 years ago (we were stopped and the van behind us didn't see that, plus I wasn't wearing a seat belt because the van we were in was a rental and the seat belt where I was sitting didn't work. I ALWAYS wear my seat belt but this one time it didn't work, but we were on our way from the temple to the wedding reception the day my brother got married so what could possibly happen to my entire family on such a blessed day???). Ever since the car accident I have had problems with my back, including throwing it out a bunch of times. I try to be careful with how I pick things up and move around, plus I have been doing a ton of core strengthen exercises for about a year now so I would think that I wouldn't be having problems. Well, I am. But what's funny is that I don't remember doing anything specific to throw it out this time. Jeff did some work on my back so it is a TON better. But I didn't work out yesterday and my workout this morning was a little weak. I just want to get back on track with working out, but my body is not cooperating!! Apparently I need a lesson in patience.