You can't increase your breast size but after the baby is born, the boobs should get fuller. I had small boobs but absolutely no problem breastfeeding. When I worked at the WIC office, I've noticed that women with bigger busts had more trouble nursing than smaller bust women. While your nursing, drink water. It'll help with milk production.
There is no way you can naturally increase your breastfeeding size. Also, breastfeeding size has no bearing on if you'll be able to nurse or not.
But i really dont like my size how i can increase it :(
I don't think your breast size matters. I've seen flat chested women breastfeed feed their babies with no problem.