Likelihood of miscarriage

I had a chemical pregnancy in September .. I had a positive test this Month at home, at the Dr and my beta more than doubled in 42 hours. I was wondering if anyone knew the likelihood of miscarriage after a positive beta test. My first ultrasound isn't until 11/28 and the lines on my tests are fading which is what happened right before I started to bleed last time .. I am nervous everytime I go to the bathroom that there will be blood 😑