Is it right to lose a best friend over a boyfriend?

My boyfriend has had bad experiences with his past ex's and thier best friends. He thinks that ima leave him for my best friend that's a guy. I've never dated or even liked my best friend in a couple way. Yes, I love my best friend but as my best friend. He's been there for me since we were in middle school and he's never walked out on me. My boyfriend and my best friend are soo important to me. I don't want to lose my boyfriend or my best friend but they dislike each other. ..so what do I do?