Ok. is it normal for one of my breast to be bigger then the other... ?

Breast asymmetry: This is normal. If you are concerned that there is enlargement of one breast due to an abnormality, then you need to be checked clinically.

Common if minimal: It is quite common and normal to have some mild asymmetry in the breasts. Moderate and significant asymmetries are less common and can be due to under development of one of the breasts due to receptor/ hormone problems in breast tissue or a congenital underdevelopment of underlying chest muscles and overlying breasts as seen in poland's syndrome etc...

Very normal.: It's amazing that any of us turn out as symmetrical as we do. If you have any associated symptoms like the asymmetry is enlarging, pain, redness, or a mass, this is abnormal. If the difference is large enough to bother you, consider a consultation with a board certified pastic surgeon to learn your options.