I'm in the middle of class and I have to change my pad but at that time I can't go to the restroom I'm also sad because I'm barely age 10 and on my period please help me someone. Tell me what should I do .And I want nobody to know

Maybe you should just go to the nurse. You don't need to tell your teacher what is actually wrong, you can just say that you have a headache. Once you get to the nurse, she should be able to help. It happens often to a lot of girls so there isn't a reason to be sad.

Or you should tell the teacher in quiet what is wrong.
Also you need to figure and plan to change pads during your day.