going mad

I'm slowing going mad - this baby of mine is very colic'y and very tempermental.
We aren't getting much sleep with the incessant crying and poor feeding - last week she seemed to settle down a bit, up to 5hrs sleep at night!
Now she is really tired, cranky, posseting (vomiting) and is really hard to settle.
My god, how can the human race survive? This is the argument for contraception if I ever saw one.