As the previous poster said, it should be "married", not "marrying". If your father had been marrying for 30 years, it would mean that he began the process of getting married 30 years ago, and it was still going on when you reached the age of 15! That's a very long wedding ceremony!
Also, please note the position of your comma after "15". You had put a space, then the comma, then no space before "my". I have corrected the positioning above.