Althea - I fully feel your pain - but I must confess your post gave me a little chuckle too. I can remember, when my kids were small, actually crying over spilt milk - literally. I SO remember that feeling of exhaustion and being frazzled, that made little things blow up into enormous things.
Some of it is obviously the unrelenting nature of being the only parent in the house, in your case. And some of it is the lingering pain of Dr. Headuphisbutt leaving you. But consider, too, the possibility that your hormones aren't balanced yet. I know, in retrospect, that part of the reason I had trouble coping when my kids were little was because my Graves disease was so bad at the time.
Have you had your thyroid levels checked lately? Been missing any doses? Had a recent change in your thyroid dosage? Having problems with any other hormones? Email me if you want to talk more about it. Remember, too, that depression is a symptom of low thyroid, and many patients on T4 only meds like Synthroid say they remain symptomatic until switching to a T3-containing product like Armour. (Not all, but a definite subset).
And have you given any thought to creative ways you could take some of the pressure off while H is gone? Trade a room with a college student in exchange for some babysitting or help with the house? Have a cousin come stay for a few months? Sometimes just having another adult in the house to talk to helps.
