Are high HCG levels a good indicator that i won't miscarry?

about a week ago I had my first ultra sound, the heart beat was great (I'm 9 weeks along now, 8 weeks along then) my blood test results showed much higher than normal HCG levels but I'm not having twins, the doctor said that was a very good sign. I'm concerned because I have PCOS, I'm taking metformin, vitamin E, folic acid and prenatals so I'm doing everything I can to lower the odds, but I was wondering what high hcg levels mean and if my odds for miscarrying are low. I also heard that once you see the baby's heart beat the odds of miscarrying go down to 5%, is this true?