I love carrying my baby. My back hurts. I'm collecting information which may help. It's here on this page for myself or anyone else who may need it. I'll update it regularly.
1. Posture is an important thing for me to remember. When I check it, I notice that the wrap sits differently on my shoulders, belly and back. This site really helped me to stand correctly.
2. Taking time to wrap properly is so important. Even when the face of a baby who sounds like he's being terribly tortured is in your face making you edgy, crazy and panicky, wrap well. It will be more comfortable for longer and baby will be happier. In my book, there are few things better than a good cross wrap.
This is a great link for different ways to wrap your baby:
3. I'm not one for lots of exercise. I just never seem to remember to do it, but one thing I've started doing as often as possible is touching my toes. This really simple exercise does wonders for the lower back. It used to really hurt, but I read somewhere that you should imagine energy being released from your spine and that is what you can feel. And it doesn't matter if you actually touch your toes or not, just go towards them. (There are lots of qualified people on the web who can tell you how to do exercises properly, please find one.)