Bella if you live in the UK call 111 for free advice from a nurse/doctor and additionally they can book you in for either a same day doctors appointment or even get you in to see a doctor out of hours on a evening or weekend.
There are alot of reasons you could be experiencing the things you mentioned, too many to list and as you stated your 11 I also don't want to give you a list of things to worry about. If you want to talk to someone about things you can message me but I think you should mention how you felt to your mum, aunt, grandma, carer, teacher, school nurse, friend, sister, cousin - anyone you trust. Talking to a stranger whilst gives you anonymity isn't idea when it is a personal and health related situation. It could be something as simple as a tummy bug, your periods starting! They're the most likely but talk to someone you know and think about seeking medical advice even if you feel better now as you mentioned its happened before.
Feel better and don't be afraid to talk to the people who know you. Take care.
Sounds like you had a lot of wind in your tummy.
When you are due for a menstrual cycle, your tummy can hurt a lot too.
The ears feeling "stuffed" and the dizziness may be due to an ear infection.
Since your wrote 5 hours ago, I trust things have settled down now.
If not, make an appointment to see your doctor to check your ears.