What to do umm cause idk?

my girlfriend and i have been dating for about a month now. we see eachother all the time during school and we hang out in the passing periods. which we have 10 minutes. a few days ago, she was hugging me then she tries to get off of me and runs out the door to see her friends. her friends that are guys. she runs out and yells their name. i didnt get a love you or anything. then today, we were standing in the hallways and i was talking to my brother and his girlfriend, and she sees a guy she knows and opensher arms for a ug. no guy hugs my girlfriend when im standing there for some reason. i guess their scared. anyway im talking to my brother and his teacher comes out and tells us to leave so we wont be late. well i start walking and my girlfriend literally runs down the hallway to go hug the guy. i was like alright and walked the other way. i got mad because she knows we dont have that much time together. and i walked down and she goes "are you mad at me" i didnt say nothing to her. and im pretty sure she knows why i was mad. and she goes "whatever" and walked into her class like nothing even happened. she always talks about other guys and ****. i dont say anything cause i dont wanna break up, but with her doing this, honestly idk what to do anymore. if osmeone could please give me an insightful answer on what to do, it would be greatly appreciated,, thanks.