Is it normal that i get turned on by too small t shirts?

Ever since I can remember I loved wearing T shirts that were too small for me. When I was 8 I was in a store wearing a too small undershirt, I was embarrassed and felt like everyone was looking at me but loved the way it felt! When I was 13 I had a size 10 undershirt that barely reached my bellybutton. I never wore it out except under my shirts. Once I was wearing it in the house and my older sister grabbed the shirt at my chest and the hem of it was up to my chest. I remember looking at it and looking down at my belly totally exposed. I immediately got an erection. Her fingers gripping my shirt and the bottom of my shirt just hanging like a rag. Then when she let go my shirt it was stretched out where she had gripped the shirt. I remember pretending that girls would pull me by this shirt and how it would look like a rag when they were done. I would masterbate about these fantasies. A therapist told me that I have a shirt fetish. Is this normal?