Why can i not get a arction from a girl anymore i dont get it?

last year alls i had to do was look at there boobs and now it like no more and when i see a guy i might get truned on with i think is nasty as **** i masterbate dose that have any thing to do with it i hate it to full compasty im not gay or bio or what ever i like girls because i just liked one in the beging of the school year and she said no mabye thats why idk but im 14