My mom said, "People don't just start stuttering."

My mom said, "People don't just start stuttering." I started stuttering around a week ago. It's been getting noticable, so I told my mom about how it just seemed to start one day and I don't know how or why. She said, "People don't just start stuttering like that." So I guess I'm making it up? It reminded me of when I had a near-fatal reaction to tobacco smoke exposure and my dad said that it was all in my head. Like, no, Dad, if I inhale too much smoke, I'll die. There's nothing psychological about it.