wondering

Bakit ganon :( August 17 first day of last period ko sept di nako dinatnan, sept 16 nag pt ako negative by Sept 26 nag pt ulit ako positive na. Oct 2 nag pacheck up ako that time 6 weeks and 3 days ako according sa last period ko 8/17 then yung lumabas sa trans v nung oct 2 6weeks and 1 day si baby at need 2 weeks follow up for embryo development pero sabi ng ob ko ok lahat wala problem. Then last Oct 16 which is 2 weeks na nakalipas nung last transv ko nagpatrans v ulit ako pero dun na sa clinic kung san ako nagpapacheck up kasi that time may ultrasound daw sila discounted tapos nung nakuha ko na result ngayon lang kasi for follow up daw result si baby 7 weeks and 2 weeks lang e diba dapat 8 weeks na siya nyan kasi 1st ultrasound 6 weeks. Bat ganon? :( sabi ng ob ok lang naman daw 2 weeks pagitan pero bat ganon yun iba iba ang weeks ? need advice. Thanks po