Which baby sling?

[HolyMolyMeOhMy]

Hi all,
Just looking for some advice regarding baby slings.
I have a 4 month old who is struggling to sleep during the daytime unless I am stood up with her and rocking her to sleep. Unfortunately this is now getting quite difficult as she is getting heavier (just over 15lbs). She also often cries once put down in her cot, so am wondering if a baby sling could help?
We do already have a traditional baby carrier, and although she is happy in there for a little bit she tends to get fed up quickly and starts getting upset. Do you think this may be different in a sling and possibly help her to have a daytime nap?
And if so is there any that you would recommend?
Thanks in advance :)

[YouCantBeSadHoldingACupcake]

I have this one. I can carry my 8 month old for about an hour and a half happily before my back starts to hurt (longer than standard carrier) Its a good combination between a carrier and a sling and so easy to put on. I have even breastfed in it walking around a theme park. I am a size 18 and it fits fine.