Conversation with my bf today about a pair of female underwear in his room that were not mine

I have a drawer in his room specifically for my clothes and i go through this drawer almost everytime im at his house. i’ve never seen these underwear before ever and i know for a fact that they are not mine. im not sure if I can trust him anymore because i’ve caught him doing other stuff such as texting his ex gf behind my back and telling his bsf that he’s tempted by other women pursing him. I’m not really sure if they’re old or not.