When I was 14yr old I was having a baby but it die. And now I am 27 yr. Old and still can't have a baby what can I do. Please help

Be healthy, & see OB. So sorry for your loss, and your situation. I would advise you to consult with an ob-gyn, and have a full exam. They most likely will want to review any details about your first pregnancy, including blood tests, or ultrasounds. Based on that information that may direct you to other specialists. In the meantime, eat healthy, exercise, don't smoke or drink, and stay relaxed and positive.
See your obgyn. There are tests that can be done to tell if is something wrong with your ability to conceive. Also to have your partner checked as well.