How do you know if your boobs are fully developed? I feel like mine haven't developed, is there way to start growth/development.

Girls tend to develop faster than boys and most females have finished puberty by age 18, although a small subset of females will continue to develop into their early twenties.  Even though puberty ends, the breast frequently will change in size over time.  The most common things that will result in breast size changes are changes in body weight, pregnancy and breast feeding.  So, if you aren't planning on changing your weight or getting pregnant any time soon, it is likely that your breasts won't change very much in size at this point in your life.

Hello,Thank you for your question. It could be that your breasts are Tuberous. This is a common situation where the tissue around the areolas is constricted/tight and does not allow the breasts to grow/round out. There is often no breast crease present and nipples can appear puffy/herniated. A consultation with  a board certified Plastic Surgeon will help explain what characteristics your breasts have and how surgical procedures can help.Be sure to select a board certified Plastic Surgeon.All the best

If you have not noticed any changes in your breasts for several years, chances are they are fully developed.  Their shape and size will probably continue to remain stable.  You can consult with a plastic surgeon in your area if you are interested in breast enhancement.