Help! Low HCG levels. Can it be successful? 2 different answers from 2 different drs.

My hCG level at 18 DPO was 103, at 25 DPO it was 135. The fertility doctor is telling me this is not a good sign and he wants to watch my HCG levels go down over the next blood drawls. I spoke to my nurse at the OB/GYN office, and she told me not to focus so much on the number but more of the symptoms. She also said to enjoy the pregnancy and that if there wasn’t any bleeding or cramping everything should be going as normal. Now I’m just confused on what to feel because the fertility doctor told me to prepare for a miscarriage, and the nurse at the OB/GYN office is telling me to relax. Is it possible to still have a successful pregnancy? I go in for another blood draw with the fertility doctor tomorrow to see if my levels went down. I am about five weeks and three days today.