I agree that it must be quite upsetting to a you, especially as you watch your friends' breasts start to bud out. Besides breast growth, you are supposed to get pubic and underarm hair and regular menstrual periods. Hope there is no delay in these body changes. If other puberty changes are normal and timely, you should not worry much and wait for some more time. However, some medical conditions, such as diabetes and asthma, may cause a delay. Hormone levels also play a role in body changes. If you are concerned about the delayed breast growth, your hormone levels can be tested. If a medical cause is found, it can be treated accordingly. It would be helpful to know your test results and also know a list of the medicines (including herbal supplements) you take.