The two things you can do is perform some exercises and use cosmetic products every day.
It can be frustrating to see your body changed and definitely not the same as before, but almost all women face it after a pregnancy or two.
But, the good news is the looks of your breasts can be improved.
There are simple exercises for breasts you can perform every or every other day. You can put your palms together in front of your breasts and push them towards one another. That should firm your breasts a bit and lift them up.
Cosmetic products are also necessary, use firming creams or gels also every or every other day after taking a shower. That way you your skin will be more elaastic and look healthier and attractive.