Why does this happen?

Jo
On the 10th of this month my period ended after having it for a week (which isn't normal to my 5 day) and now I already got my period again it's only the 29th. But that's not the problem here. But If you know the answer to that question above as to why it did that please answer. 😊
But yeah, every period first day. If I don't eat I will get really bad stomach aches, I'll become very weak, and get very hot. Literally I would start sweeting from EVERYWHERE head to toe. Oh yeah including my scalp. And sometimes when I cool down finally after 5 minutes of sweeting everywhere I'll get cold. Sometimes I feel like I'm going to fall if I'm caught standing up and I start breathing heavily. Does this happen to you guys? Is this not normal? Maybe it's because I'm skinny? I don't know 😔