Measured weeks Ahead In Early Pregnancy

Hello, got confused with my ultrasound result. LMP: Feb7 (regular mens) then nagpaultrasound po ako last March 10 so lumabas is 6wks and 2days wherein it should be 4weeks and 2days (based on intercouse). Tas nagpaultrasound po ulit next day, ang lumabas naman po is 7wks and 4days. Kung yung unang result ang susundin, normal po ba ang 2weeks ahead? First time here. Nagdadoubt kasi yung bf ko. Huhu ?