Best way to lose weight when you have a bad back?

[TaliZorah]

I'm 5"7. I was 135lbs before pregnancy and 150lbs at the end. I'm 7 weeks post and now 140lbs. I'm eating 1,500 calories a day and trying to walk 3 miles, however some days I can hardly move due to back pain. It took me 2 weeks to lose 1lb! I can't join the gym obviously as I'm being investigated for back issues and can hardly lift anything.

Any advice for how to lose when I'm limited in what exercise I can do? I want to get to 125lbs.