Is being loved as nice as it seems?

Lately I've been having some problems with a guy. He loves me very much and he keeps saying if Im happy he is happy. But I don't understand that at all maybe its because its my first time being so deeply loved. The things he says doesn't make sense to me how can you say "if you die I'll die" about someone you've known for half a year?? Why do you want to spend the rest of your life with me and at such a young age too (17) isn't that such a big commitment? And wy does he cry when Im mean to him? Such a cry baby! So yeah i don't understand this at all.