Pregnant with a toddler

Hello everyone, I'm currently 12 weeks pregnant, 2nd pregnancy, I'm already suffering with the fatigue, nausea ans stomachache. I feel constantly angry and on the edge of explosing, I get angry and irritated very easily at my hansband and my 4 years old toddler. I dont know why I cant manage this, I'm always yelling at my kid (who has already issues with late speech), she is becoming very irritating, I mean normally she is a nice who listens but lately I cant recognize her screaming and throwing tantrum alla the time it's making me sick, I yell at her every single time it's becoming a vicious cycle, I'm even more concerned that this may cause regression when it comes to her speech issues. I'm not sure if kids at this age become difficult or it is just her and is it related to pregnancy. I really don't know what to do.