Today I had two ultrasounds at different clinics. The first one said t…

Today I had two ultrasounds at different clinics. The first one said there's a heartbeat, but it's faint. The second one said there's no heartbeat, and everything matches the timeline. There are no bloody discharge, just a slight pain in my lower abdomen. A week ago, there was a heartbeat. I think there might be toxemia, since I feel nauseous all day and can't eat. I don't know what to do ? Could it be that the ultrasound is wrong or that the machines are old? I'm really worried now. This is my second pregnancy, the first one was a miscarriage at 7-8 weeks.