Unless you need to know to track some disease, its absolutely irrelevant.
Try living in the here and now instead of worrying about body counts and who has more experience. Enjoy the person you are with and dwell on that instead otherwise you are only hurting yourself with your imaginings and both parties lose. Unless they are cheating on you at the moment, why does it really matter? If they are, move on. If not, such concerns will only sabotage you. Grow up. Everyone has life experiences, baggage they bring along with them. Why let that spoil what could be a good thing?