How to tell my sister im deeply in love with her?

I guess it started at age 11 and she was 14 and now i lover her deeply. we would sleep in same bed and she would let me put my upper leg around her hip as we sleepd and i would get an . I feel in love with the smell her beautiful long hair and puting my arms and legs around her as we sleeped. When i would be in same bed with her if felt like my brain was melting and i could not controll myself from falling in love. Now im 15... i have deeper feelings for my older sister i lover her so incredibly...Now she hurt my heart in the worst way... And now inside i have fallen apart. Every night i go to bed i have emotional brake downs... looking at her picture every night wishing we could be together for reasons i dont fully understand.... Mosty nights i cant sleep worried she might fall in love with someone instead of me... All this pain and suffering over started from her boy friend of 2 months whom i hate with a deep pion.... I cant take to see them together... i kno i can treat my sister better then him. I feel like bashing her boys friends skull in with a hammer as he sleeps next to my sister every night... he took away everything from me. I feel if she ever fell in love with someone instead of me i would not beable to handly it, i lover he to much to see her with a differnt man. As i feel the clock ticking down....tick tock in my head... i cant bear to see them together... feels like im out of time to do somthing about her boy friend.... i just cant stand him any every minute im losing my chances of my sister feeling the same way about me.... Tho i do understand theres a chance she will never feel the same way about me... tho i feel most take a chance on telling her... i dont fully understand my emotions and why i feel this way. I guess i come on this website for... your guidance on this... sad screwed up story about my emotions that i cant control.