My XP is still using ours. DD is 16 months, 11kg. Have you tried putting DD on your back? Much easier to carry that way...

I think what made a difference with me is that i used it all the time, everyday, until she was about 9 or 10 months old, i have a meitai i made now, but because i used it so much i got stronger as she got bigger and never had that OMG moment. I've not used it now for about 3 months and i'm sure if i tried i'd be in agony! LOL. They sell pretty well on eBay though, if you want rid of it.

HTH

Bx