He's throwing off mixed signals! what do i do?

im a high school teenage girl with boy problems..... typical! ok so there's this guy i like. he flirts with this girl named natasha all the time. he stopped me in the hallway one time and told me he liked me and that he used to like her. he said that the only reason he talks to her is to bug her. I have gym with him on mondays and he NEVER speaks to me. he is ALWAYS sitting with her. Then when we got called tot he auditorium he was walking beside me and he looked at me and smiled. Then he told me he wasnt going to ask me out until my ex boyfriend moved on....( my ex still seemed attached to me,...but i wasnt). the next day i told him my ex moved on and asked another girl out. (which was true). he said "ok, meet me at lunch and we'll exchange numbers". so we did and its been a week and he hasnt called me. WHAT DO I DO?!?!? does he not really like me? does he like natasha more? do i forget about him? HELP! :(