Ok so there is this girl who likes me but I don't like her and well I kind of been leading her on and I didn't mean to and I don't want to hurt her because we've known each other a long time and I don't know what to do I need help!

The only thing you can do is stop leading her on and be a little stand-offish. After a while she will be able to tell that you do not have that type of feelings for her by reading your bod language. If this does not work, you might just have to tell her you got carried away in the excitement of things but honestly don't have those kind of feelings for her. Just be very straightforward with her and don't BS around... thats very confusing to us gals! You sound like a sweet guy for caring about this girl's feelings! Good luck

Tell her the truth and break it to her easily