You show all the classic signs of being transgender and if it takes a little more to convince you, go to Youtube and request "the transition channel". This is a series of videos that will show you what therapy sessions will ask you. This will help you be more sure of your decision and maybe make you a bit more comfortable facing your parents.
One of the regrets I had was that I didn't have the option available to me that you have. At 15 there was only one hospital in the United States treating transexuals and it was no where near me. When I started treatment, I ended up in Southern California, the closest treatment I could find. By the time I was on hormones I was about 26 years old and most of the damage had been done. It cost a good deal of time, money and pain undoing what nature had done to my body and I was one of the lucky ones.
I really can't tell you what the cost is because there are so many factors involved and I was never on blockers (they didn't exist when I needed them). Common dosages are cheap, insurance reduces the cost even if it doesn't cover it and seeing your body hasn't seen much puberty yet, you may need a very small dose.
If you decide to tell your parents, we can answer your questions and provide you with an education. We have a number of letters available that you can learn from or present to your parents if you think you will have problems saying the words. We are even willing to talk with your parents if they need to talk to somebody about it. I understand some parents don't take it well and your screen name tells me a good deal about your upbringing. Sometimes religious parents accept this and other times they don't.
One thing you haven't ask that you should understand about yourself. What you have is a birth defect. Before you were born your brain wasn't exposed to male hormones at the right time and you developed a feminine brain. There is nothing that can be done to give you a male brain or fix it. The only solution available is to match the body to the brain. People fight the feeling but it never goes away unless you receive proper treatment. I haven't felt what you feel since before I had surgery. I now feel completely comfortable with my body and my life.
As for the people on the site, they are pretty friendly and helpful regardless of the direction the are going. At some point in our life, we have all felt what you are feeling which makes us brothers and sisters. Close to 50,000 people have made accounts on this site at one time or another so you have become the member of a very large family.
Make sure you ask any questions you might have. I am in Arizona and am pretty much available in the afternoon and evening hours to answer your questions. I may drop out for a short period of time but I will be back.
You are welcome and I enjoy helping you because I hope I can help you avoid some of the difficulty I faced in transitioning.