Does he like me?? 10 points for best answer?

so, there's this guy mark in my school. he's in my homeroom and science. Ever since the beginning of the year, he's been fake flirting with me and embarring me. And i could totally tell he was faking it. ..... for the past 2 weeks, he's been acting weird. He's been staring at me a lot and flirting with me FOR REAL . and wen i was in the hallway, one of his gal friends, whose usually really nice to me and stuff, and she told me in the hallway seriously that mark liked me. do you think he likes me? And i really like him too. How should i act? cuz i get nervous a lot. should i smile wen he looks at me or wen he talks to me? WHAT SHOULD I DOO ??