I would suggest you to see a gynecologist. One of my friends is a gynecologist at cloudnine hospital, & as per her suggestions "periods are must as they prepares your body for pregnancy each month". An average normal cycle in most of the cases appears after every 28 days long. And It ranges anywhere from 21 to 35 days in adults and from 21 to 45 days in young teens. But It should be there hopefully every month or atmost after every 45 days. So I would suggest you to go for a gynecologist soon.
It's super common to have a very irregular period at your age. It takes several years for your cycle to settle in to a normal schedule that can be tracked. I'm sure if you asked your friends about it they would tell you they're having the same thing with not knowing when to expect the next period.
So although it's so annoying because you never know when you'll get it, it's totally normal to have this happen.
I remember being in 7th and 8th grade and getting my period randomly while at school and not having any supplies with me! So I ended up leaving some extra pads and an extra pair of undies in my locker in a cosmetic bag in case I ever had an issue and I was glad I did. But believe me I got embarrassed several times back in those days because I was unprepared and had no idea when my period was going to come next.
Hi, I am also 13 and at first I had a irregular cycle. So I talked to my mom about it and she told me that we might consider seeing a gynecologist. She also said that sometimes when you are younger it's normal to have irregular periods. Hope this helped!