Why did this happen when my boyfriend M22 hugged me F22?

I F22 have been dating my boyfriend M22 for 3 months. He is awesome and I love him. He knows that I’m uncomfortable when it comes to physical touch and connection with people and has been very respectful of that. Tonight I let him hug me while we watched a movie. Once the initial shock from human contact wore off, I felt very tired, almost intoxicated or narcoleptic like I could fall asleep right then and there. Why did this happen? Can someone please advise? Thank you. It was not unpleasant. Just different.