Why did this happen?

July 8th I was 9 weeks pregnant.  I started to bleed alot...i saturated my pants,and bed and passed some tissue.  I went to the dr and we did 2 Hcg tests.  The first one was 75000 and the next day it was 51000.  Therefore my dr confirmed I had a miscarriage.  Then last week i went for a routine physical and while palpating my abdomen my dr suspected i was pregnant.  Ultrasound confirmed that i was 16 weeks.  What does  this mean?  So I did not actually miscarriage despite the blood tests or is there a possibility that i was carrying twins?  Im confused and upset as for in the interim I had severe back pain.  Seeing as how i believed i was not pregnant i took anything and everything under the sun to try to alleviate the pain.  My dr was even giving me medications (amitriptyline, pregablin and T3's ) as he was starting to suspect that my pain could be due to MS.  Now i am extremely worried that my prescription drug use has harmed my baby.  Please help...thank you!

[Yao Sun, MD, PhD]

Although you ask some very important questions, as a Neonatologist I do not have the specialized knowledge to answer them.  You need to discuss your questions with your Obstetrician or with a Perinatologist.