Hi I got my period about a year ago and I never found the answers to these questions.

1- Why do your feelings change and you become more moody?

2- Why does hair become more oily?

3- Why does acne show up more?

Please and thank you for answering.

Im 13 by the way

Because of your period and also during pregnancy and menopause, a female body is flooded with hormones, thus all those problems (and more you didn't list) show up.

Your feelings change because of your hormones in your body that change the levels of stress and happiness and that

I haven't noticed my hair being oily yet tbh

And you get spots because again hormones , try lookings hormones up I don't know how to explain them but its meant too happen there's nothing wrong with you its just something every women goes through

These are all because of the hormones your body starts to release once you start having periods. It is completely normal and is because of your natural hormones your body produces.