Legal Question in Family Law in Pennsylvania

How would it be used against you? There are no Heart-Balm causes of action in PA (actions for alienation of affection or criminal conversation). Do you have minor children? Do you have custody? Will they be exposed to someone you are just dating? This could conceivably affect any custody if that is an issue.

Will you be seeking alimony? If another man was cohabiting with you after a divorce this too could affect that. Otherwise, I don't see how you dating would be relevant.

PA still recognizes fault based divorces and adultery is one of the grounds for that, but I don't see how post-separation dating would translate into adultery during the marriage as it would not be the cause of any marital dissolution.

I suggest that you go and consult with a family law attorney. You will need one for the divorce and to help adjudicate any other issues like child custody/support, alimony or the division of your marital assets and debts.