I mean it's hard when you get to your twenties, right? To find someone who hasn't had a few partners before, slept around a little bit, and had a couple of one night stands. So, does it bother you? Obviously no-one likes thinking about their respective other with someone else, but is it something you can easily block out?
What if things are around that you remind you of it? Love letters they haven't thrown away, photographs of them, and so on. SPILL, people.