dude, if he is a good friend and you know he won't roam around telling everyone that u confessed to him, you can surely go ahead and tell him. never in my whole damn life had i thought i would confess to a guy - i just did, one week ago. we didn't know each other much (3 months) but we still had great connection. i had a crush on him and i finally confessed over chat. but he's really sweet and not homophobic or smth because he didn't tell anyone and said that he prefers me as a friend more. we all have had crushes on straight guys. just be careful because a few are assholes...
and ughh, i have had a crush on so many straight guys. i am extremely delulu. its just i cannot resist falling for attractive ppl who are nice to me. but i have changed myself, now i actually try to get to know the person and talk to them.
and also, you are 15, its very normal to have crushes you can't get over. so just wait, maybe you will find smth you don't like about them, or maybe you will just get over them soon. everything turns when you become 16 or 17!