Anyone else's SO lock bathroom doors?

Ra
My boyfriend has the habit of locking the bathroom door when he's taking a shower.
Is that weird?
We've been dating awhile, and recently lost our baby due miscarriage, but I don't know.
I don't close the door and leave it open and my boyfriend invites himself in to wash his face or brush his teeth.
Even when I was pregnant, he would come in while I was using the bathroom and have conversations with me.
Why does he lock the bathroom when he showers, but never when he uses the toilet?