AHH so the question is that one of your parents are a BT.
That is not the same as a major health issue. It is my impression that in many circles that is not an issue at all. In more heimish circles it is more of an issue.
It is fair to assume that anyone who is dating you knows about your background or, if they has wanted, could have found out with ease.
I would suggest mentioning it causally on the 4th or 5th date.
It is also worth talking over with a rabbinic figure.