I need to know if this is normal and if not am I going to get taken seriously this soon?

I gave birth four days ago to my second, the birth was amazing I loved it, I was home within two hours and I was on cloud 9. I was eating fine, sleeping fine and not in any pain at all I’m even back in my jeans, sounds perfect right? Well I look fine on the outside but in my head I dont feel okay. I’ve had nightmares of my first born having a stroke and being brutally hurt by paramedics that I’m waking up crying. I’m too scared to sleep, im scared that there’s someone around my house or if I’ll start seeing things, I’m scared of being alone, I don’t even want to bath by myself. I have no worries about my children and I’m completely fine in the day but as soon as the evening comes i start feeling this way. I don’t want to talk to anyone because my husband isn’t so supportive this time around and my mother will keep on about how I feel and I don’t want to be reminded. Obviously if this isn’t normal i will get help but if it’s normal after birth then ill try and ride it out.