Why WOULD HE DO THIS TO ME?! :( 10 POINTS!!?

I am 19 dating my 23 year old bf for 1 year. He used to be so attentive, called me 5 times a day, talked to me on the phone for hours, drove 25 minutes one way, to see me everyday... now he barely calls, doesn't care to see me as often... Are we slowly drifting apart? :(