Thanks so much for reaching out for help in thinking through your sexuality, it took a lot of courage to be open and honest about your feelings! As you go through this process, you should listen to what your head and heart are telling you, that will always help you find the answer. You mentioned not being able to tell anybody but if you can find a adult, relative, teacher or guidance counselor that you can trust, you will be able to discuss your sexual exploration.
As you said you have always been attracted to boys but now your focus is being physically feeling drawn to women. It is very common at your age to have a physical attraction to both boys and girls. You may also feel emotionally connected to both genders and that is ok too. On http://www.bisexual.org you'll find a lot of helpful information on bisexuality. If you click on resources, then bisexuality-general information, then "Bisexuality 101 from PFLAG" you can find information that may help. Another great resource is an article called "I Think I May Be Bisexual, Now What Do I Do" www.advocatesforyouth.org/component/content/article/724-i-think-i-might-be-bisexual-now-what-do-i-do and here you will see many people that have gone through the same feelings as you are going through right now.
To talk more about your questions about your sexuality, please know that you can call the Trevor Lifeline at 866-4-U-TREVOR 24 hours, 7 days a week. A great please for you to explore is is Trevor Space which is an online social networking site for LGBTQ youth who might have had the same questions as you do. It's a supportive community where you can be yourself and learn about others who are going through the same process as you.
This is an ongoing journey for you and try to stay positive through it all! Always know that at The Trevor Project we are here for you every step of the way so you never have to go through it alone.