When do you call it quits

We just discovered that my husband has ADHD which explains so much, but his first appt with the psychiatrist isn't till 9/1.  I'm at the end of my rope here.  I don't know if I can make it.  We've been going to marriage counseling which now seems like a waste of time since it wasn't geared toward helping us with one of us having ADHD.  His stress level is high and therefore his temper is terrible.  I feel I can't talk to him.  He goes from 0-10 in a second.  We have a three year old and I have to think about him and what this is all doing to him.  We're constantly fighting and its not right.  I don't know if I have the strength to stay in this... some advice please