In today's America, it would be very surprising to find a newlywed man or woman without a sexual past. Fundamentalists preach "just say no" and don't let their girls use birth control. As a result, there are more pregnancies among the "just say no" crowd than in the general population. These cultural differences aside, let's just assume that both the man and the woman have a sexual past.
In the ideal situation, both partners would be secure enough not to be bothered by their mate's sexual past. At the same time, it seems that it would be smart not to delve into either one. One partner may be secure about the relationship and the other may not. One may have had a rather promiscuous past and the other may have been more monogamous.
If either partner is greatly concerned about or curious about the other's past, to the point where it is an issue in the relationship, there may be a problem. If one partner likes to talk frequently about their past sexual adventures, there may be a problem. If your partner likes to talk about past sexual relationships and it bothers you, just tell them that you would rather not hear about those experiences. It may or may not mean you're jealous. It may just mean the topic makes you uncomfortable and, really, it's a bit thoughtless to bring up past relationships unless it is relevant to the subject at hand.
Talking about your past sexual relationships can give your partner ammunition for your next "disagreement." Past sexual relationships should stay in the past. There really is no benefit to sharing them and there could be a lot of harm. Every couple needs to work on their relationship in the present. As the Bible says, "Sufficient unto the day is the evil thereof." Deal with what is happening in your relationship today and don't let the past get in the way.