although back carry doesnt work for every child. DS for example has only recently decided it is ok to be behind mummy, and even now he only stays there for maybe 30 minutes (he is 17 months old). have you tried a hip carrier? there are several available that are quite comfy. DS is 14kg & i carry him in a sling on my hip often.
getting down on the floor to do fun things is also a good plan - what sorts of things is your little one interested in? our DS has always been into "vrooms" so playing with cars etc on the floor interested him. pegs was also a favourite at that age. i remember tho that he went thru a period where he wanted to be carried more often than not - tiring at the time, but it has now passed & he just wants to get down & run run run!
