Hi Herman,
it possibly could be gynecomastia - google it for technical information. Gynecomastia can be due to hormonal disturbances or side effects of some medications - are you on any meds? Breast cancer in a young man of your age is virtually unknown, if this is your worry.
You really need to go back to your doctor for proper evaluation and treatment. Have you talked to your parents about your lumps? I am sure they will be concerned and get you to a doctor. It is not an emergency, but needs looking into.
Take care,
Liz.