Gym Cl AHHHH?!?!?!?!?

Okk so I'm in 9th grade and 10th period- Gym Cl- is hell!!!!! I just dont know why I'm so scared to participate....I look at the clock like every minute...I'm serious!!!!!!! I'm just like really really REALLY bad at gym....and so the teacherr like yells my name I think at least 40 times during cl!!! And she says that I might fail gym because I dont put enough effort....but I jusst dont know how to put effort when I'm soo bad...it's sooo embaring!! How do I overcome this fear of gym clas--- its the worst period of the day!!