I didnt have a bump til I was about 28- 30 wks and its only been the last couple of weeks that its now visible to strangers through my clothes ( am 38wks and having c section tomorrow ) I have all my normal clothes still except I have gone up 1 trouser size just so they sit on/ above bump and not under it as cant stand draughts.
My baby is small and so am I but I was very fit before and all the midwives comment on how tiny and neat my bump is.
I think it all depends on the individual person and how well you are.
Ive not been well throughout but the last month have been really quite ill, in and out of hospital, am on strict bed rest and literally have nothing left to give to baby hence why they are doing a section tomorrow before my body packs up completly.