Ame SF,
You're a really good writer, and I enjoyed reading your post. I'm very happy for you. You came out to your sister, and she responded in a positive way. It is interesting that she suspected you were gay before you even said anything. Sounds like you have a good relationship with her.
Like you, I discovered my sexuality in my teen years. For a time I believed that I was possibly gay. I was in love with my best friend, who was a girl, and I had very strong sexual feelings for her. Now I am married to a man, who I love very much, and I really enjoy sex with him.
Ultimately, I recommend treading carefully with the rest of your family until you are free and clear of them financially speaking. Given your sister's reaction, they are likely a more understanding bunch. Also, I recommend focusing on your future plans--college, trade school, career--before jumping into a serious relationship. I recommend this to all young people irregardless of sexuality.
Hugs to you, Ame.