Woman caressed my bf's hair right next to me

Last night my boyfriend invited me over for some drinks at his job meanwhile he worked (he's a bartender.) After everybody left and they finished cleaning up they sat down to count the tip money. An older waitress sat down next to him on his left and I was sitting on his right. I was looking for Airbnb places on my phone because he and I are going on vacation next week so I wasn't paying attention to my surroundings. When I notice the waitress is caressing his hair and he laying his head on her shoulder, telling the story about why he likes it (his mother use to do it when he was a little boy.)

I got furious!!!! I told him "I thought caressing your hair was something intimate that only I did to you hair. Thought it was exclusive. You tell everybody why you like it done? Every person you know does that to you?"

He responded "calm down. She's old. And it is something intimate between you and i"

The waitress is about 50+ yrs old, very nice lady! It's nothing personal against her. It's simply the fact I thought only I did that to his hair, he openly does it at work so I wonder where else he does it. And many other things.

I said hypothetically speaking if another (older) man were to do that to me would he be OK with it? He said absolutely not! So why is it okay for me to be OK with another woman doing it to him? He could've laid his head on my shoulder but he didnt....

Previously that night I found out he had deleted the msg chat with his babymother so I wasn't able to see what he had messaged her. Few days earlier he had gotten extremely drunk and doesn't remember what he did. That is why I wanted to see the chat. Keep in mind he never deletes anything. Ever.

Am i overreacting with being mad his coworker caressed his hair?