I did my ultrasound on my 5th week. ..all they can see is a gestation and a yolk sac ....but at least made sure that its not ectopic
In your 4th week, all that can be seen is a slight thickening of the uterine walls, and in the 5th week not much more than that unless you happened to ovulate right on the dot or a little early. If you happened to ovulate just a bit late in your cycle compared to average, you won't see what you expect and will get unnecessarily stressed. Try your 7th week or later.
This is very early. I went at 6 weeks and left very nervous and upset because they couldn't see baby but could see yolk sac. Went back at 8 weeks and everything was perfect!
The first ultrasound is normally around 10. They make sure there is just one growing and measure baby and will give you a more accurate due date.