Um, okay, that is actually a huge red flag and literally none of his business what you wear to bed. Like, who does he think he is, your dad? It’s super weird that he’s trying to control something so small and personal, and honestly it gives me the ick real bad. You should wear whatever is comfortable for you.
If you like sleeping in panties, then you sleep in panties, end of story. It’s your body and your sleep, and if he’s getting weird about it, he’s probably got some major insecurity or control issues going on. Girls have to deal with enough crap about their bodies without their own boyfriend dictating their pajamas.
You need to put your foot down and tell him to back off about your clothes. If he keeps making a big deal out of it or tries to guilt-trip you, I’d seriously reconsider dating him because it’s only gonna get worse. Don’t let some guy tell you what to do, especially in your own bed.