I'm 13, and have anxiety. I am freaking out right now and I need help?

Okay, at the end of last year I was diagnosed with anxiety. It was so bad I had to get out of athletics. I'm in 8th grade now and got back into athletics. It just seems to be getting worse though. Getting out of athletics last year really helped because it stresses me out ( I have blisters from stress ). I want to get out again but everyone at school will make fun of me. My mom tells me that I need to just try my best? I am crying right now because i'm freaking out so much, I cant sleep because of it and sometimes I cant go to sleep until 3 in the morning. Please help me. What can I do about this?