what should i do for having a flat stomach but not having the size of my butt changed?
I exercise 2 hours every day including aerobics,swimming and working with dumbels, i have a flat stomach but also my butt is turning from the round shape into a flat shape too,but i dont want that to happen,i mean i want to have a slim body butt .so what should i do ? should i avoid doing a particular exercise for having that kind of body image? something like tyra bank’s ?how is it that their body is big size in some areas but slim in others?
Weight training only increases the size of the muscle. If you want to lose weight you need cardio. (Swimming is GREAT cardio) If you want to decrease the size of your tummy do things like Pilates. You can buy pilates videos that have on the menu "Abs" "Buns" "Arms", etc. and you choose which one you want to work. It all just depends on the excersize you do.
Always remember to eat healthy and take vitamis, that increases your results. Tyra is a goddess by the way! 
Hope I helped.
Crunches for the abs.
If you lose your butt, get it back with lunges/squats.
I do other things, but I don’t know the name to it. Just do what makes you feel good.
Actually, look up this vitamin. It’s a natural breast enhancement herb but in a lot of cases [and myself] it has made "butts bigger", so basically gain more fat only in that area. It’s called ‘Maca’. You could also try ‘Saw Palmetto’ but I have never tried it personally. Maca made me bigger and more rounder in that area in which I regret because I was already nicely sized there :/
Anyway I suggest it. It’s only like a few bucks for a bottle of them.
Good luck.