Has anyone else had this happen?

On Monday I had my ultrasound and found out its a boy! However, they want me to come back in 3 weeks because they couldn't measure his heart and brain because of how he was laying.... The Dr said everything looks good- they just like to get all the measurements. Has anyone else had this? Was everything okay? I am thinking if there was something wrong with his heart they would have picked up on it by now . . we have heard a strong heart beat every appt - always between 153 - 156. The more I think about it the more worried I get.

I had to go back for them to get the back of the neck measurement because she was lying with it curved and they never could get her fingers. So sometimes some pics/measurements are hard to get.

He was laying on his stomach with his heels up by my belly button...the tech had to tap on my stomach to get him to even move his legs so we could see what he was. I just get a little nervous!