What Causes Overwhelming Anger During 33 Weeks Of Pregnancy?

Hi! I m pregnant with my first baby, 25yr old and I m about 33 wks now. I ve been pretty stable emotionally throughout life, and during my entire pregnancy besides a very occasional tear or two which i realize is irrational and hormonal. Why I m concerned is lately when I wake up in the night, I am waking up FURIOUS, I don t GET furious, I wake up in that state. I know in my mind that it s irrational and I try to calm myself down, but it s overwhelming anger and rather unnerving because it is out of character for me. My mother has a very severe case of Skitzophrenia and I may be becoming paranoid but wondered if you could give me a tip/ information on how to prevent this. I m so worked up at the time I awaken I could punch a hole in the wall... and i really don t like it. It is very very weird for me.