It needs to start with your wife. It is she who needs to establish boundaries with people. If she's keeping herself available, there's not a thing you can do but leave this marriage.

This pregnancy is a major red flag. It's not your fault you have a low sperm count. There are ways to get pregnant without resorting to deceit.. and she chose a "donor" she's in love with.

If you're wanting to stay, I'd consider marriage counseling.