I'm regretting being reckless and  fooling around with one of my best friends recently.
Well it's over now right? Is it going to affect your friendship?
I wouldn't care if I hadn't seen him in a few years, the only reason why I still do is because we were friends since childhood.
You are allowed to fool around with anyone you like as long as it doesn't hurt someone down the line. Being friends with benefits isn't likely to last long, but be open with your friend about your feelings and intentions to stay friends.
I probably won't confess my real feelings to him though.
Don't you think he is wondering how you feel? It would likely make you both feel better if you just have and honest chat and clear the air.