[James98]

Since you are living with him, I think it is important to tell him. He will already wonder what you are doing and you owe him an explanation. Don't ask him for his opinion, just tell him what you are doing and why. If you ask him, he will tell you your breasts are just fine the way they are, even if he would like to see them bigger as that is the safest answer. He will not want to risk your relationship by suggesting there is something wrong with your breasts.