Shana-chan,
Test for a female breast: Lie down on your back. Place the fingers of your right hand flat against the left breast, fingers over the nipple, with your left arm extended above your head. A female breast will have a round or oval lump under the nipple extending towards the outside of the body that is distinct from the nipple. You should be able to move the lump with your hand, independent of movement of the nipple. If you are in doubt, see a doctor and get a mammogram. Fat tissue appears clear. Female breasts have lumps in them. If you have glandular tissue, you have female breasts but still may not be intersexed. Many young men, as they enter puberty, develop small, female type breasts (gynecomastia). In most men, they go away as they get older. No real help for your question. It could just be you have fat deposits on your pecs or you could be growing a pair. Knowing what they are doesn't get you very far. You need to know why they are there.
My experience: However, I had a mammogram in 2011 that showed only fat. In 2012, a second mammogram showed an increase in the quantity of fat (even though I had lost 70 pounds) and an increase in connective tissue within the breast. Then, I got the glandular tissue; which was due to an increase of estrogen and a decrease in testosterone, which was due to a medical condition. So, I started with doctors. Somewhere in there, I also saw a psychologist. I realized that I was trans. I am still working on the medical condition. And yes, it is serious. But I did start HRT and now, on HRT, I have real breasts.
Intersex conditions: Depending on how you count, and I like the way I count, there are 26 intersexed conditions. Which one would you like to discuss? (Rhetorical question....) It takes a medical professional to get that answer.
Serious: I put intersexed conditions under the transgender umbrella. It's a big umbrella and includes all kinds of people. You say you want breasts? You may be transgendered. Start by talking with your parents or a doctor about your breasts and that you are concerned. (Parent will probably blow you off so be persistent.) Questions to ask are ones like "Why do I have them?" Your goal is to get to a medical doctor and to get to a psychologist to talk with both about your breasts and at least with the psyc, why you want them bigger.
There are a number of medical conditions that can cause a person to grow breasts. It would be good to know what is causing that as some are serious. Being transgendered is difficult but being what you are is also difficult.
We are here for you.
Jen