I have been seeing this guy for 2+ years and we have both expressed that we are each other's absolute best friends and love each other and wish we could always be together. But whenever I bring up taking it to the next level, he says it wouldn't work, that we have to leave it just the way it is. What gives?

Hi
So when you say the next level what exactly do you mean??

Yes good question. Where are you now and where would you like to be.
Please explain your current relationship a little more in depth!