Spotting 😔

So my period was oct 4 I had light spotting when I went to the bathroom on Thursday evening and I started spotting when I wiped it was very light as well I went to the er bc I’m like omg I’m having a miscarriage I go to the er today bc I had cramping but the bleeding was really light brown n just tapered off I ask the doctor what’s going on they said possibly threatened miscarriage 😔😭bc they didn’t see anything in the ultrasound but my hcg levels on Thursday was a 207 today it’s 506 could it be a possibility she is wrong n it’s implantation bleeding or is she right n I should prepare for the worst? 😭😭🥰