Feeling worthless and defeated

My boyfriend decided to wait to shower 10 mins before my therapy session started, he was aware I needed him to watch our twins while I was in session... Anyways, I'm sitting there with my headphones 🎧 on having session and I hear him mutter to my son, your mom is too careless to change your diaper, how long have you been this way?!?! He had 💩 but I had just changed him before session then he was jumping in his jumperoo and my boyfriend heard him cry but yet blames me for not changing him on time!! I always attend to the babies while he's in session and even when I'M cooking!! He knows I was busy, he hurt my feelings making me feel like a horrible mother! What an insensitive asshole ugh 😫😔🥺😭 I'm trying to do better and proceed with therapy but he's making me feel I'm a useless mother... What do you all think? 🤷🏻‍♀️