are you still studying A levels?
academic stress is really really hard!
that is great about your friend, they seem really nice, you've started a support network which is great!
When you are anxious, it definitely spirals out of control, like you say. It is like a domino effect, everything becomes more intense around you. For noticing breathing, it can be really hard to stop the cycle.
Have you noticed anything that usually starts it up about the breathing, i.e. if you are alone it is more likely to happen?
The dizziness then becomes a product of the over-worrying and it is horrible!
To combat this; i think what would help is that you talk to people about this feeling where it most prevails i.e. at home or at school (teachers/parents), or if you call your GP describing this feeling and asked to be referred to CBT to learn techniques to help your anxiety.
Anxiety is the worst, i can understand how scary it must be for you right now.
I struggle badly with anxiety too, my PMs are open anytime
Anxiety comes in bursts, soon you will find a coping mechanism and this feeling will go away. You are doing great!