Thanks for the advice. I will start trying the warmup you linked, as well as doing some pilates before lifting each time (which I stopped one or two weeks before injuring my back).
I'm back in the gym again, but squats and deads are not feeling so good, so I'm going to make some changes to how I work out as well as drop the weight on squats and deads and work back up. Because I used to feel so ruined after just the squats and not have much energy for other exercises, and so that I can ride my bike around again (without my legs feeling like lead from squatting several times a week), I've decided to workout three times per week, and break it up like:
1) Squats, pull ups
2) Bench press, overhead press
3) Rows, deadlifts
This way I'm in and out of the gym in under an hour, so I don't feel stressed about spending extra time warming up/cooling down, and my body doesn't feel as wrecked afterwards. I know it isn't supposed to be a good idea to alter the 5x5 program, but I'm still doing all the core exercises, I'm just doing less each workout and progressing more slowly.
Squats: 20x5, 40x5, 50x5, 70x5, 80 4x5, 70x5
The last set at 80k didn't feel so great, so I dropped back down for the last set.
OHP: 20x5, 30x5, 40k 5x5
Bench press: 20x5, 30x5, 40x5, 50k 5x5
Row: 20x5, 30x5, 40x5, 50k 5x5
Deadlift: 40x5, 60x5, 80x5, 87.5x3
I stopped short of the last two deadlifts because I felt a tweak in my lower back, I'm going to drop the final weight back to 70k or so next time, same deal with squats. Advice on this new plan appreciated!