Who to Chose and What to do

I have a girlfriend right now but idk,like I love her so much but lately she's been rude to me and not acting like herself and I met this boy kind of,like he's my sister's ex boyfriend and he's 16 years old and like I already like him so fucking much like he's so sweet,kind,gentleman like,respectful,respects girls,he's cute (really cute),flirtatious,and just really amazing.Like I don't even know what to do anymore! This is all fucking driving me crazy and fucking insane!