You won't be his first, his last or his only. He's loved before, he will love again but, if he love's you now what else matters?
He's not perfect and neither are you. And the two of you will never be perfect but, if he makes you laugh, at least once, causes you to think twice and admits to being human and making mistakes.... Hold on to him and give him all you've got!
He is not going to quote poetry. He is not going to be thinking of you every moment but, he will give you a part of him that he knows you can break. Don't hurt him, don't change him, don't expect too much from him.
Smile when he makes you happy, cry when he makes you sad and miss him when he's not there....