RE: Is it too late to start using a sling? And sizing question
Definately measure yourself. I doubt you need anything bigger than a medium. Kristin, the owner of hotslings is also very helpful with sizing. I am afraid that the Over the Shoulder Baby Holder, which is what your sling is, gets mixed reviews. The padding on the edges (rails) and large amount of fabric can be intimidating. Try it out, though, it may work well for you. I'm sure I could use one easily now, after 11 months of slinging, but it might have been harder in the beginning. It may be easier with a bigger kiddo, like your 5mo old, than with a newborn.
Tarah
Mama to the Forrest Creature 3/04 and Baby Ber 4/07
"All true wealth is biological" Cordelia Naismith Vorkosigan