Ask your mum how she faired with pregnancy usually stretch marks ect are more prone if your mum had them as elastin in the skin can be hereditary my mum never got any except her boobs my sister never got any except her boobs and mum had 2 kids my sister had 1 i myself am having baby number 5 and have no stretch marks exept for on my boobs when my milk came in and they ballooned and as for the belly that also depends on how big you get how many babies are in there and my belly is normally flat and firm and i have had 4 kids already i put on 13kgs with my 1st and 8-10 kgs with the others the day after their birth my belly was almost flat but felt very spongy and squishy for a week or 2 i am not a big person i am normally a size 10 but am solid my weight seems to go to my hips and butt so after birth i have usually dropped 5 kgs the day after and it takes 2-3 months to be back to my previous weight.
But just remember it takes 9-10 months for your body to change so it will take a while to be back to normal.
I am having a c section this time around so i wonder how my belly will look after the op fingers crossed i am lucky this time also.