My wife is so nasty and moody from 3 months pregnant to now that our son is 15 months old.?

You know it is possible she is suffering from some form of depression, like post-partum depression, she may need some professional help and that is nothing to be ashamed of. I am 34 weeks pregnant and I was just put on antidepressants by my midwife because I was having some problems which in turn was causing problems in my relationship. Good luck.