my 7 week old boy's belly button looking big when his stomach is empty. is this normal ?

A. the child is having umbilical hernia which is very common in children and goes away by maximum 2 years of age. with growing age it regresses anxd goes inside it does not require any intervention or treatment before 2 years if itx is non complicated. meet your doctor once who will tell you whether any intervention or wait and watch policy is required.