What do you do when you fall in for your best friend?

we been friends since 4 years and just became Best friends year ago. He's the only guy iTrust he tells me everything iDo the same and lately we became like a couple iDon't know why but iGet jealous when he talks bout girls. he randomly texts me he miss me and we talk on the phone everyday. My friends said when we look at each other we look like we are in love. What should I do ?. because iThink if we do go out it mess up our friendship?