I'm 15, and I feel incredibly stupid for thinking all of this. ?

You're not being dumb. You truly care about this boy. Love is love regardless of when it is or who it's with. Enjoy your relationship with him and see where it goes. Don't get all serious and heavy about the future though. Neither of you can know what will happen in the future. Getting too serious too young is a relationship killer. Good Luck to you Sweetie, and God Bless.