Anger issues

Saphinah • 26 years old, first pregnancy, excited but always anxious.
Since becoming pregnant I've become a really angry person. If anyone threatens me in any way I square up to them and tell them to hit me. Deep down I want them to hit me first so that I can beat them up. I work in a betting shop so I get threatened a lot just for doing my job. I usually bite my tongue and let the people have their rant and just let it go. But these days I'm ready for a fight. To the point where last night during an argument with my younger sister she threatened to throw her phone at my head. So in turn I got in her face and told her to do it so that I could punch her in her face. My mum had to pull us apart and locked me in a different room until I had calmed down. I don't understand what is happening with me. Is it a maternal instinct to want to protect myself because I'm pregnant? I know it doesn't make sense that I'm pregnant and trying to fight people. But I literally only get like that when I'm threatened with violence. I'm not usually like that at all. I don't condone violence and I've never been a fighter. Have any of you ladies experienced a sudden change in your temper? It's scaring me a little because I could get myself seriously hurt or worst still I could get my baby hurt. I need help.