Seeing part of your fear can be a trigger. When I used to struggle with homicidal OCD, for example, knives would be a trigger. When I wasn't around any trigger objects, the thoughts were -usually- not as bad. Likewise, someone with pedophilia OCD may be triggered by seeing/hearing children.

These past experiences you have had as a child that are normal, but were made a big deal out of by your mother, could have also been part of what led to you developing POCD in the first place. Our anxious brains are quite good at finding what frightens us most, and amplifying it.