Unless u get a boob job after ur done breastfeeding or a boob lift its impossible it's natural and normal way of life u kinda have to deal with it.. U can always wear pushup bras I found the push up water bras are best
You can't completely prevent it, but wear a bra a much as you can stand it through the day and that will help some.
There's exercises that help lift afterwards nothing to worry to much about mine got great volume during my workout after I quit breastfeeding but the will not b what they use to be that's forsure
What kind of workouts did u do!?
Is their a specific way that's best to dry up your milk when u don't want to breastfeed any longer? I just let it dry out by them selves not doing anything which to forever w my last 2 pregnancies but I feel like that didn't help my breast volume at all! Lol
Dumbbells at the gym worked great so many diff way u can work those muscles with them pull em up hold em out n strengthen everything in that are push em up hold your arm out with an n open n close ... theres a specific machine that works out your arms n targets those muscles that will enhance the sides of your peck area ... push ups against the wall all those will work great Consistency is all u need to strengthen it up u can train your body to be however u want... Goodluck
I was told wearing sports bras smaller than ypur boob size helps alot, and i i can honestly say it truly has.