Why aren't I hungry?

I know that when you are on your period you can get super hungry but I have been getting less hungry like for lunch I used to have a cheeseburger, tater tots, a rice crispy treat, a mini bag of chips, and a carton of milk( I'm in middle school ) but today I had a rice crispy treat and a carton of milk and this has been happening for a while and I also have little to no breakfast so I don't know what's going on