Why do I always freak out when someone touches my hips

Back when I was in highschool I knew a guy who used to always jab me in the hips and make me jump because he thought it was funny. Now whenever someone touches my hips I always scream and jump. It just happened today when my friend tried to move me out the way. Is this just like PTSD or something or is this a normal reaction I don't mind being touched anywhere else