It's awful when you feel out of control and think that your actions have harmed others so you have all my sympathy.
I suffer from horrendous PMT(have resorted to several diff methods to get this under control but no luck so far) but DS2, 4, seems particularly sensitive to my moods and state of mind. My periods seem to ahve affected him from when he was a baby. Just a thought that your DC may be picking up on your PMT?
Having said that imho your DC are old enough to realise that their actions have consequences just as yours do.
Part of growing up is learning that life doesn't always go your own way; if the situation has got this bad for you over when they have their lunch it sounds like they know exactly what buttons to push to wind you up.
Start over again tomorrow and talk to them about how things that happen to your body, (mine all know about periods as I'm constantly followed to the toilet and gave up on the idea of privacy years ago!) affect you physically and your mood too.
Explain simply about lack of patience, sadness, etc. Let them know that it is not their fault that you feel this way and that you are soryy that you all ahd a horrible day.
Choose something easy for them to do to help you. Tell them hot water bottle helps and cwtching up on the sofa with them would make you feel better too.
Its hard.
I can say this to you now, but it'll be a real struggle a week from now, when my PMT starts, to take my own advice. I hate that my moods can have such a huge impact on teh whole family
Take care, don't be too hard on yourself x