Tara,
I found mine hard to use at first aswell, Nathan sounds like he was the same size as your bub at the same age, although he was born 59cm, lol.
It is all trial and error til you find the most comfortable position for you and your bub. At first I found that my babies got lost inside although I lined the bottom of the sling with a folded nappy, (Cloth one, lol)this helped not only boost them up but was great for moving baby up into the right position. I breastfed my babies and went shopping hands free, it can be done, you just have to adjust it to fit you. I still use mine although I put Lissy (2 1/2) in it and push Nate in a pram, probably neeed to swap them over now that Nathan can climb out of the pram and Lissa will stay in it now. lol.

Practise wearing it around the house and yard to work out the best position for you both. My DH loves it he takes it out when we go out together, he likes to wear the baby as he said I did it for 9 months it's now his turn, Lol.