Vaginal Ultrasound w heavy bleeding

I’m 4 weeks if that... I went in today for spotting which she believes was implantation. She was able to see the yolk (barley) and the sack. She said to come back in a week that she thought things were ok. But I got home and literally an hour later and I started bleeding like I started my period. I can see it drop when I pee. I also need a liner ... I’m 100lb and size 2 idk if the bleeding is due to me being so tiny??? Is this normal for some or do I need to get in my mind that I’m MC again, as I did last month .... ?? I’m not having cramping or pain. I’m having some back pains and lower belly cramps after the ultrasound but that was normal.