Found a pair of used female underwear in bfs apartment?

I found a pair of used underwear in bfs apartment. I was doing my normal rounds of vacuuming and stumped across a pair of used underwear. I had been gone for the last 5 days on a work trip. He has only lived in this city for a year, when we first started dating I helped him unpack, get new furniture, and organize everything. When I sent him a picture of the underwear asking who’s they were he responded saying, “oh the underwear in the closet, I saw those and though about throwing them away, but wasn’t sure if they were yours. Within 30 mins of sending the photo he had come home from work and canceled his meetings. Don’t you think if you weren’t guilty you wouldn’t make it such a big deal. He has been begging me to believe him, but my gut tells me he’s lying. I clean the apartment all the time and yes maybe there is another explanation but I’m going to need the truth rather than “they must have been stuck to my clothes”. I also helped organize and unpack all his clothes so. I just need advice. He’s making me feel like I’m in the wrong for not believing him.
Found a pair of used female underwear in bfs apartment?
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