I had severe anxiety and panic attacks when I was pregnant with my fourth. It was bad as we'd had a loft conversion that dragged on and took 2 months instead of the agreed 3 weeks! We had to live elsewhere with 3 kids under four and moved back home only 2 days before elective C-section, all very worrying..so I couldn't sleep and it was an awful time! I had to have counselling, which really helped. (now we have 6 kids and I still panic from time to time!)
As you have to wait to see your doctor I can say this for now - allow yourself to go into "survival mode" and only do what's necessary! The rest can wait. Cancel appointments, meetings, phone calls, anything that can wait and allow yourself to slow down. it will get better, but you need time to figure out how to cope ! it's annoying to cancel stuff, having to say no and make up excuses, so just say you have too much going on right now - which is probably true.
If you are starting to actually hyperventilate, try to breath in and out into a paper bag or even a towel. I just use my hands formed into a bowl! (it slows your breathing to inhale back what you breathed out, stops you from getting too much oxygen in blood etc)
Concentrate on counting to 7 as you are inhaling, then count to 11 as you are exhaling.
7 in , 11 out. repeat and focus on the numbers only. and again and again. push all other thoughts out of your head and just concentrate on the breathing and counting.
when you have calmed down, you will want to do everything, but just choose 1 simple thing or the most urgent.
you could also try and make a list of all do things you must do (forget for now the "want","would like to" and "should do"!) so you won't forget the important things!(sorry, I know it sounds simple, but writing list helps prioritizing...)
With help I realized my biggest problem was time management and the sheer amount of tasks to do be done.
So ask yourself questions - does it need to be done now? do I have to do it? does it have to be done at all? if not, leave it and move on, no need to feel guilty!
I hope this is helpful
And try and ask someone to help you with school run if possible.