Hey! Welcome! And great job so far.
Calorie counting has been working out pretty well for me so far, even though I'm not really doing exercise at all. It's much easier for me to not eat the calories than it is to do cardio. :P
That said, have you talked to your doctor for exercises that would be good for your back? If you have back issues there are some exercises that could really help you build range of motion, and increase the strength of supporting muscles so you don't get as many problems.
I have problems with my middle back, and I know that when I do the exercises I'm supposed to do (admittedly hardly ever), or when I'm in better shape in general, my issues are much much less.