What's really good for lower back pain is just lying on the floor. Really, hear me out - I learnt it as part of Alexander technique on a course but just generally it's good.
Basically, it involves lying semi-supine on a hard surface, ie. flat on your back, maybe with your head on something to lift it a bit and your knees up with your feet on the floor like this: /\__o
It hurts the base of your spine at first but really, if you lie like that for a while your body will sort of flatten out and you feel so much better when you get up. Seriously, give it 10-15 minutes.