My best GUY FRIEND may be my HIGHSCHOOL SWEETHEART...?

i am developing feelings for my best guy friend. i think we may be highschool sweethearts because we are almost always together. we have 5 out of 8 cles together during school, we always hangout with each other on weekends, like go to movies, play putt putt, go bowling, hangout at each other houses. if we are not together then we are talking on the phone. i think i am starting to develop feeling for him but dont really know how to let him know..any suggestions?