CS Scar Pregnancy

Hi moms. I'm getting paranoid because of the result of my transV ultrasound. I'm almost on my 7th week of pregnancy and I was told by my OB that there's only a 50% chance that this pregnancy will push through because it seemed that the gestational sac was planted near my Cs scar which can be very dangerous. Anyone who had the same experience or have experienced CS scar pregnancy? I was advised to have another ultrasound on Monday to know if this pregnancy is viable or not but I want to know if there were cases that the result of the ultrasound changed after having told that you might have Cs scar pregnancy on your first ultrasound? I know there's a little chance but there is still that 50%.