The Clue period tracker allows you to enter details about your cycle so that you can easily see when your next period is due. It is free on Android and IOS. Unlike many of the other period tracker apps it is not bright pink, nor does it look like a kindergarten game. Clue also has a website with many articles and videos, some of them specifically for pre-teens and teens. I particularly enjoyed Erica Avey's article, Advice to my 13 Year Old Self.

If you're in high school then you are either in the middle of exams or they are fast approaching. Most likely you are fairly stressed and anxious. Just remember, you are not defined by the score you get at the end of year 12. For the sake of your mental health, schedule in time to do things you love. Doing this will put you in a better frame of mind and the time that you do spend studying will be more productive. There are some ideas above if you're stuck.

We have lost track of healthy portion sizes - sometimes one fast food meal has your whole daily calorie intake. 
Here are some websites to help you make better choices about what you eat:
https://www.nhs.uk
https://www.gethealthynsw.com.au 
https://www.makehealthynormal.nsw.gov.au 
https://www.eatforhealth.gov.au