Welcome to PC CloudsAtNight. I too know those fits of hysteria when things just build and build until you just explode. I know you think and feel like you can't cope but you can and you will. One way or another you will weather the storm for your child and for your husband and for the life you have that you want to live to its fullest.
You have come to a good place to find people who know your suffering and can help you through the 3 weeks until your appointment. It can help to know you are not alone.
Wishing you well.