oh arte - you poor thing. at least you are a FABULOUS mum - even if you are bored.
TBH i dont think i could do it, i know i would struggle with it... thats part of the reasons i havemade the choices i made (which i know are not for you).
Have you thought about an online course or smething like that? or something in the evenings?
would it ever be apossibility to share sah and working with DH - if it is important to you both that a parent is at home with your kids maybe you can share that?