Serious Question

Love

Sooo found out I was pregnant. Planned Parenthood did Blood test HCG was 72.. they said it was really low so they gave me an ultrasound but they didn’t see anything So they did blood work again 2 days later HCG was 36 so she says they r ruling it a miscarriage.. All of this happened almost 2 weeks ago. So the day before yesterday I POS it’s positive still. My levels should be negative by now and I still feel the flutters and things in stomach. Is it possible they were wrong? Should I go to the doctor? I don’t know what to do. This was my first pregnancy