Question

Brittany
Ok so I am 15 wk 4 days and I have not heard the heart beat yet I have only been to dr once that was at 13 weeks I also went to er for bleeding at 5 weeks they saw a sack but that was all my hcg levels were really high so er said maybe twins I don't know yet bc I have not had an ultra sound since well my question is this I should be high risk this is my 5 th pregnancy I have an 8 year old who was born at 27 weeks a 4 year old who was born at 32 weeks and a 2 year old who was born at 37 weeks and a miscarriage in July at 10 weeks shouldn't they have do an ultra sound and listen to heart beat by now ? I am scarred I have an ultra sound for feb 2   By then I will be 17 weeks I am just scarred