You just have to believed in. I survive maths exam while suffering the ache that caused by my period time.
Math was given for 2 hours. My stomach ache start a couple of minutes before the exam was started. And while I was doing the ache is still there in my belly. 15 minutes before the exam ends, THE PAIN WAS GONE! and I was like hgsdfdhkgthjsgfgjdfdgdgfht. Okay, today was perfect day. Super duper hard math exam with period ache.

Note this, you can relief your stomach ache in your period time by doing math for almost and hour. It'll work on 30 minutes of time.