Hello I Have Endometriosis Well My Last Period Was August

Hello I have endometriosis well my last period was August 11th but I don't overlate for 5_6 weeks sometimes well I had spotting two weeks ago and went for a scan Friday to be told I lost baby everything was seen but a f/h apparently baby measured 8 weeks but I don't know what to believe as the sonographer had the US zoomed out all the way through is there any chance there could be another reason why he didn't pick up f/h and I have three children already all three were small for there dates please help is there any hope he could be wrong and would second opinion be healthful