I met my ex when I was 19... we broke up when I was 28... we were together almost 10 years. We grew apart... like you and your BF we were young and then as we got older we drifted apart and tried to keep it going... eventually the differences were too much and we were not able to overcome them. Don't let 10 years go by girl. Sounds like you & him are outgrowing each other... that is not a bad thing. Its just time to move on. Your BF now does not know what 'FOREVER' is (the long haul) yet, he will get over it all and move on in his life as will you.
Don't stay if you are not happy, this is YOUR life to live... dont let him pressure you into something that does not make you 100% happy! In the end you'll still end up leaving him and it will be MUCH harder than it would be now. Trust me!
I wish I left my ex when we broke up when I was 25. Wish I never went back! Instead I put another 3 years into it, only to be 28 (almost 29) and starting over. Now Im 31, still struggling to get over it, am jaded, don't trust men, afraid of commitment, afraid of getting hurt... UUGGHH! Yes I want to get married, but I dont let ANY guy NEAR me! When they try to get close, I dump them and run!
Good Luck! and BE HAPPY!!