Girl trouble :(?

need help with a girl becasue im a freshman in highschool and i really like this girl but im not totally sure she likes me back. but the delema is that shes pretty popular and im making my way up there becasue i was a new student last year. also whenever i talk to her i always get a felling and i look somewhere else and not at her. it as im being a different person as if a was with one of my guy friends. also if a do talk to her a dont want to look like a jack, so can anyone please help me out