Girlfriend Trouble!?

i got asked out panicked and said yes now im in love (not joking i think about her day and night i even hav dreams about her and she and i are going out with the wrong people) help! dont say im too young cuz i love this person with a pion that no one has ever seen in any movie or drama well thats the thing i know i have my whole life but i feel that i want to spend my whole life with her! so i need to know what i should do wait and risk the chance she will leave before i can tell her or break with my gf and steal her from her boy? I love her to the ends of the earth. i would even die for her but she doesnt know that i need real help! dont tell me het a life cuz i hav one and i love her but my gf and her bf are getting in the way! help! she likes her bf out of desperation i think but yah i love her to death and she thinks im just her friend1 but she is almost the only wun i hav so if i ruin our friendship i will be lonely but i will go crazy if i dont tell her how i feel. I Love You!