Thanks for coming to Alterheros with your question.
Bottling up feelings and not being able to tell your friends who you are can put a lot of stress on yourself. However, I want to let you know that you're not the only one experiencing this situation. I know some of my friends in high school went through this as well. Also, I don't think there is anything wrong with being bisexual. I don't have a set answer as to what you should do. Everyone has different ways of coping and dealing with situations in different environments, but I would suggest talking to counselors at your school, your parents, or someone that is really close to you. Letting out your feelings that were bottled up inside would really help if you feel that you need to get it off your chest. The people you choose to talk to shouldn't and wouldn't be disgusted with you or judge you, because they are the people that truly love and care about you. There's an old saying those that mind don't matter and those that matter don't mind, that really sums it all up.
Your sexuality doesn't change who you are on the inside and people that really care about you would know that, so don't be afraid to talk to someone that is really close to you if you need to. You are still very young and time is on your side. Keep reminding yourself that there's nothing wrong with being bisexual and there are many others that are bisexual as well. So take your time to figure things out, and along the way you might find others that are having the same feelings you are currently having. Don't bottle things up if you don't want to because there are professional counselors and school psychologists that are available too if you wish to talk to one.
I hope that helps. Please keep asking questions if you need to.
Zhen, for Alterheros