Could anyone give me an example of a cute love letter to send to my boyfriend?

Wouldn't really be from you if we show you an example so best thing here would be to write one from your heart to him. There is no right or wrong here as long as it comes from you and is true. You can do it. Ill give you a start here, "I love you more today than yesterday but not as much as tomorrow"  so take it from there. Good luck and write what you feel in your heart. Good luck