Low Confidence; Scared i'll get made fun of.?

-Im not a fast runner...im really not. Im not fat, im average. I dont have a HUMONGOUS stomach, but i do have some tummy. Anyway, this wendesday I have to do 100 mm, and last time i couldnt do it cause i was sick, but i still watched everyone do it. And all of the girls got 18 seconds. So since last week ive been practicing my running, but i always get 20 seconds.



Its embarrasing, and I dont want people scoffing in there mind thinking im some fat ***. Oh and i have a really low stamina; i run out of air super quickly, so i have no idea what i'll do for 800 m. Im really really really scared, i dont want to do it at all, and i know for a fact im going to get made fun of.



Is there any way i can boost my confidence for this? And just boost my confidence for things in general?



Please please PLEASE help :(