The very best for back comfort and long carrying with absolutely no discomfort for mom and very comfortable for baby is....
baby trekker
I owned both regular baby bjorn and bjorn active, the active one gets my vote between the two because of excellent back support but you can really only use it comfortably until baby is about 2 and then after than baby's legs grow usually too long so when you walk with carrier on baby's legs hit your legs.
And the bjorn active is very expensive.
the baby trekker is very reasonably priced, can be used from birth to 40 lbs and my ds is now 35 lbs and 3 yo and we still use it when going to grocery store. The baby trekker saved me at MCO last august when there was security delay at check-in and we couldn't move for 30 minutes while they sorted things out.
I was so grateful to have the carrier because my son would never have stayed in 1 place for those 30 minutes, not in my arms or in stroller and airport security didn't let anyone move. Many parents were struggling with 1-3 year olds who wanted to walk or go to the washroom. My ds was very comfortably resting in my baby trekker.
It's very very comfortable, can be worn on front or back and folds down into really small sack that can fit into any bag or in base of any stroller or on handle bars of any stroller. Can't do it with the bjorns.
I've owned baby slings, hip carriers, infantino carriers, snuggli, ergo (wasn't that great and my ds was 2 at the time)
Anyhow, the padding used on the trekker makes this one so very comfortable and you will not regret your purchase. You can buy them second hand or directly from manufacturer in Canada.
www.babytrekker.com
Your back will not hurt- guaranteed.