You shouldn't be big at all. At five weeks pregnant you have just developed an embryo. An ultrasound typically will not even be able to detect a heartbeat yet.
If you mean 4 weeks after conception the embryo is about 1/6 to 1/4 inch (4 to 6 millimeters) long.
24 weeks
it takes four weeks for the organs of an embryo to form..
how big is the embryo when you began to hear its hearbeats?
An unborn baby that is less than 8 weeks old, is an embryo, after this it is classified as a foetus.
Your baby is 15 inches long and about 3 pounds!
8 weeks
10 weeks.
Fetus
A fetus.
Twenty-six weeks is six months.