Your question is one which is important and relevant especially now, during the month of Elul, when our focus is supposed to be on tshuvah. There is an explicit halacha which states that a person is forbidden to remind a ba'al tshuvah about his past. Putting a sinful past behind you and moving on is difficult, and is more difficult when it comes to more serious transgressions. A ba'al tshuvah is considered a new person with a new chance to do things over again in the eyes of halacha, and aside from people he has hurt directly, whom he has to compensate in some way, no one should remind him of his past.
This task is particularly difficult for a spouse, who would like to share in an open relationship and sometimes prove their love despite their partners past. The best way you could show your love and trust in the new person your husband has become is by allowing him to leave his past behind him and seeing him as a new and whole person, the person you fell in love with and married. By really seeing him as a new person, you don't have to feel self conscious about anything he did in the past, which should not reflect on the man he is today.
We wish you ktivah vachatimah tovah, may we all merit to become real ba'alei tshuvah.