Found something in my boyfriends closet

So I was doing laundry the other day for my bf while he was at work so he’d have work clothes, I was picking up clothes off his closet floor when a pair of underwear (not mine) fell on the floor, I took a pic and messaged him asking who’s underwear were in his dirty clothes. He answers back that he thought they were mine because they were on the floor of his moms bathroom ( when we have to shower we use his moms because the other shower is currently broken) then he goes “are they my moms?” Uh no your mom is way bigger than me . Anyway turns out they’re his moms boyfriends daughter, she’s 6 and a bigger girl I’m teeny tiny so we’re probably about the same size. I apologized profusely when he got home and he said he understood because it looked bad and he told me not to feel bad cause he knows I have trust issues and baggage and he understood why I got upset, so I guess I’m just trying to say my Boyfriend is so awesome and I feel terrible