OB wants me to get blood test for dating

shanpren

My first appointment isn't until November 14th, but the nurse called today for a routine interview and was thrown off because I had my Mirena removed on Sep 15th and never had a period.  I was charting and counted Sep 15th as day 1, and clearly ovulated on October 6th (temp increase and + OPK) but they're totally uncomfortable with that. 

Is it wierd to have me in for to test my HCG levels to date a pregnancy?  Doesn't that number vary from person to person?  It doesn't seem like looking at that number could really help them date a pregnancy very well.