Need boy advice!!!

I really like this boy as as a friend, we have such a close relationship however he wants to take it further. I have told him no currently but he still wants to take it further and thinks we will go somewhere. Normally I’d say yolo (cringe) and get with him but I don’t want our friendship to be ruined. Also the idea of kissing him and doing stuff with him kind of grosses me out since I’ve always been so close to him as friends. What do I say to him without it sounding like I’ve led him on or our friendship being destroyed?