My boyfriend also said he does not believe in love, but he didn't know what it meant. In relationships we have different love to the love we have for family and friends. It is very intimate and scary and it is easier to just pretend is doesn't exist. Your bad moods and not talking to her seems like emotional blackmail and you don't feel special to her because both of you are scared. Could she be trying to make you jealous with the flirting with other guys? She sounds insecure. I think both of you have experienced hurt in the past and need to address that hurt and move on into love and intamacy. I hope you make it.