If I was you I would just ask him nicely 'can we just continue as friends?' If he is nice he will say yes.
My boyfriend is my best friend. In a small town friends are limited! He's a great best friend, but he isn't a very good boyfriend. Breaking up would end our friendship, something I don't want to lose at all HELP?
If he is the best friend that you say that he is, you should be able to talk about anything. Talk to him about this, and come up with a solution together.
I'm not sure what you mean by "not a very good boyfriend". If you want to be just friends then have a serious talk with him and say you value him as a friend and don't want to lose him which could happen when romance is involved.
Maybe your boyfriend/best friend also knows that it isn't working out. Just talk to him and let him know that you can feel there isn't something right on the romantic level and that you think you make better friends than something romantic. Maybe he agrees and will feel relieved to be able to take a step back.
