Unplanned pregnancy

First of all, I am lawfully married and I have 2 kids already. Still in my 20's First and second child is planned pregnancy, a girl and a boy. My husband is totally fine with my third pregnancy but not me. I feel very tired and I just... I don't think I can handle it. I've been having this thoughts about giving up... I don't know. Anyone had unplanned pregnancy? What do you do... I'm so stressed up. Please advice me