Why is a heating pad bad for a woman ?

my dad saw me with the heating pad this morning and told me if i keep using it for my cramps iam not going to be able to have kids in the future (iam only 20)...i have been using the heating pad in addition with taking pain relievers or naproxen from the doctor for as long as i can remember..maybe for about 7 years....but is this ture???????does the heating pad do some damage to me that i wont be able to have kids?