Why? and how?

Because you don't love him (yet)
he is maybe just saying it so you keep dating him.
The word love is used far to often, I don't really think he is in love with you since you are only dating
But maybe he is and really falls for you

My opinion is, you only truly love the person you will end up marrying. Most of the time, it's infatuation. You don't love him, you might in the future, if you marry him. But, for now it's only an emotion that doesn't have the right word. Yes I know, once you're boyfriend and girlfriend saying "I really like you" is what you say before you date. But throwing the L word around casually shouldn't be done. I fell for it a few months ago and found myself drowning in tears, especially since I was in denial since he told me he loved me and said that he PROMISED he'd never leave me, and that he wanted to marry me.
Be careful!

I really feel like that too .

i think maybe its because there's nothing in the relationship for you to entertain you or motivate you enough for you to tell him you love him .
x