Please help me

I'm about to explode. Im almost 8 weeks pregnant. Here's why I'm about to explode. Me and my fiancé needed to do laundry so we went to his grandmas like always. His family still doesn't know that I'm pregnant. His brother and his brothers kids were there too. No biggy. I didn't care. I never do. But then my fiancés niece started hitting me in my stomach and I kept telling her no but she kept doing it. So I went outside and tried calming down. Once calm, I went back inside and sat down again. His niece yet again comes up and starts punching me in the stomach again. I kept telling her no and not to hit. The thing about these kids is that they don't get disciplined. Never been spanked a day in their life. I don't care about his brother and sister in law's parenting techniques but they do need to learn that they need to respect their elders. After awhile I started having really bad pain that was at a 10. I texted my fiancé and told him but he didn't care. He told me to "put my big girl panties on and suck it up". That's where I got pissed. I'm growing his child in me and he blew me off. I told him that his niece was hitting me in my stomach and he didn't care. This caused a huge fight to break out at his grandmas. After awhile I made him take me home. Within minutes of me being home I felt a gush of liquid come out of me. I ran to the bathroom and checked what it was and I fell to the floor balling my eyes out. It was blood. My pants are ruined and the underwear I had on are ruined. I texted my fiancé yet again and told him that I was gushing blood. He told me to leave him alone and deal with it on my own. I layed on our kitchen floor crying and holding my stomach. He didn't get home till hours later and by then the bleeding had stopped. Our fight continued and he told me that he wasnt gonna tell his family about me being pregnant until he's ready. We agreed to tell them after our appointment on March 2nd. Should I be mad that he doesn't care about if the baby is okay? Should I be mad that he doesn't care that his niece may have caused us to lose a baby that we tried for? Hes making me feel like it's all my fault and that it's my fault that I was bleeding and in pain. Hes never acted like this before. It's to the point that I wanna leave him because I no longer know the man that I've been with for 3 years. I love him to death but I'm also starting to hate him. What should I do guys?? Talking to him doesn't work, he just yells at me. I'm so lost right now. He told me that if I kept up my "attitude" he was gonna turn me into a scared little girl. He basically threatened to hit me. I know his words and I know that's what he meant. Just please help me guys. I'm begging. What should I do? I'm terrified of him now.