How do I turn a f*** buddy into a boyfriend?

I've been good friends with this guy for a long time and we started to like each other and back then I told him I didn't want a boyfriend I just wanted to have fun ;) we have been having fun for a few months now and it's been great, but I'm starting to want more. Should I just break things off with him and try and find a guy who wants a serious relationship or should I try and make my f*** buddy my boyfriend?
How do I turn a f*** buddy into a boyfriend?
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