Ex-Boyfriend's friend, my best friend? need to get it off my chest.....:(?

Have you talked to him about it? If you have then have you had feelings for each other before or is this the first time you have thought about kissing each other? you have to talk about it of or it will be awkward. You were most probably just vulnerable and craved comforting which he has given to you before, it could of been a one off and it that case just carry on as normal and don't let it affect your friendship :)