<human>: Give me a shortened version of the text

I've been with my boyfriend since I was 18. He's my first love, and my first long term relationship. I do love him. We rarely fight, we have fun together, he's my best friend. We have a happy, healthy relationship. But for the past several months, I've sort of been thinking about breaking up... I don't even have a completely solid reason why. He doesn't treat me badly. I'm not miserable. But the future is really scaring me - we don't live together, though we probably will within the next year. I am happy, yet I wonder if I'm happy enough. I keep wondering what else is out there, and even though we are very similar there are things I feel like I might want in a relationship that he doesn't have, and the thing is, I've had such little experience, maybe I DO want to end up with somebody like him, but I don't know that because I haven't really seriously dated anyone else. 

Then there's how completely overwhelming it is when I think about how drastically our lives would change if we did break up. He's been in my life for 5 years, we share so much at this point. How am I supposed to just, never talk to him again? Also I know he'd be crushed... would it distract him from school/work? How could I do that to somebody I love? Should I "take a break" for a while, and see how that goes first?

Has anybody else gone through this, and if so, what did you do? Are these normal doubts, or does it indicate real issues? I'm absolutely terrified of making the wrong decision and losing him forever, but I'm also terrified of continuing to stick it out and then it's a 10 year relationship I'm having to move on from. Part of me feels a reckless need to just break it off and make myself fight through the pain (and possible regret) of it just so I can relieve this emotional turmoil I'm in.

Thanks in advance to anybody willing to offer any advice.
<bot>: Not sure if these persistent doubts about my 5 year relationship are normal or not, and if not, how on earth do you just end a long term relationship?