Last two major tips when carrying in a wrap:
The first step to avoiding back pain before even putting your baby into the wrap is tying it nice and snug (the wrap shouldn't have any slack in it and feel like a tight t-shirt).
After placing your baby into the wrap, make sure the fabric is extended to the back of your baby's knees and that baby's bottom is higher than your belly button but lower than baby's knees.
These steps are key and while your baby faces you, will bring the load closer to your core and better equip your body to carry your baby properly.
Happy back= Happy babywearing!