please help I'm scared nd going crazy

I just left hospital and almost in tears of what my dr said! My last period was feb 8th no dr confirmed that I am pregnant! He checked my blood quant and said it's at a 150 nd said that's low nd did a ultrasound and said he couldn't see anything but I'm still early on! But I just looked online nd seen that my blood quant is normal basing on lmp! I'm scared because I don't want to miscarry !