I didn't really need to change much clotheswise until I was about 24 weeks or so - it was pretty annoying as I couldn't find any maternity clothes that actually fitted until about 30 weeks - especially jeans.
This time around I am already starting to notice it - I am more prominent in the belly region - especially when wearing my bodysuit for netball. But still I haven't "popped" I would say give me another month and I'll be digging out the maternity clothes