They can tell, but maybe you should tell your family first before the doc says anything, how old are you that they would have an issue?
No. It's impossible to tell if someone has had sex just by looking at them. Doctors can make assumptions but they cannot tell or prove a woman has had sex by looking at her vagina.
If that were the case, my doctors would have believed me when I said I was a virgin when I was given my first pap smear at 18 and again when I had my second one at age 21.
Girls' hymens break by things as simple as playing as a child, riding a horse, etc.