I am 23 years old female, have a small breast size. I want to increase the size naturally through exercise, diet or massage. Please suggest.

No can do! Breast size is genetically determined. The only way to get bigger breasts "naturally" is to gain a lot of weight: never a healthy choice. Breast size is larger with pregnancy and breastfeeding temporarily. Surgical enhancement is a pretty safe procedure when done by reputable plastic surgeon.