Two year old suddenly afraid of the darl after spending a week at BM

I'm the step parent in this situation. My step son is almost 2 and splits his time between our house and BM's. He is usually great about going to bed with our usual routine which is bath, pjs, brush teeth and either read a book or listen to some of dads music. As soon as we asked him what he wanted to do tonight and he starting sobbing. He told us he didn't want to go to bed and is scared. He started clingling to me and my heart broke when he asked if i'd protect him. He had a full on panic attack about going to bed and i dont know what to do. We turned on his bathroom light and we will be getting him a night light tomorrow. My mind just wonders what the hell is happening at his mothers house for it to be such a quick difference. She is now married to a guy that we have only met a few times. My step son has been acting weird when we pick him up and when we go to drop him off he starts crying and asks to stay with us. I'm honestly torn i feel like I'm overthinking it and the other half is thinking the worst. via /r/Parenting https://ift.tt/2JqNXc1