does sucking your own boobs contribute to breast growth?
Yes it does! This is why inducing lactation can cause breast growth, even before milk is present.
Sucking your nipples (or pumping them) not only causes blood to circulate through the chest, but it also signals the brain to send vital sex hormones to the area. Together, this will cause your boobs to expand.
Not only does it cause breast growth, but it also causes nipple growth as well. Because the nipple is being stretched and sucked, your nipples will swell and also become more sensitive!