It probably does have something to do with him, but I would also avoid saying that you're not attracted to him. You could even tell him that he is an attractive person when you break uo with him. You probably wouldn't have gotten started with him, if you thought he was ugly or repulsive.

For whatever reason, this connection is just not happening for you, and there is no requirement that you, yourself, know why that is. The chemistry just isn't there. Looks probably isn't the main reason. But you don't need to insult his personality, either.

You do need to end it, since you really are not interested in him. I don't know if you should even wait until Friday. He'll be thinking he has a date Friday, only to find out that you're done with him. I think it would be more fair to call him today or tomorrow, at the latest, and cancel getting together with him Friday. You could say that you are needing to back off because you are not feeling the connection that you hoped would be there. You could also thank him for showing an interest in you.

Whether or not you might be lesbian is really not his business, at this point. I would not go into that with him. I think most people know fairly early in life which gender they are attracted to. If you feel you aren't sure, yet, you don't want to label yourself prematurely. Some psychologists claim that being truly "bi" is very rare, and that's what I happen to believe. But keep your options open until you have more experience with life and with people.

There really is no totally pain-free way to reject someone. But you haven't gotten deeply intimate with him, yet, so it's not like you've hugely misled him. He's probably already figured out that you are not wild about him. It might be okay to meet with him again to talk, if that's what he wants - after you explain that it won't be a date.

A main concern that guys have is that a girl might talk bad about them, after breaking up. It would be gracious to assure him that you won't be doing that. You could say that you respect him and that you have only good things to say about him. After all, you wouldn't have spent 6 weeks with a guy you thought was a jerk.