you were a teen and had been in the Foster system for years and had numerous traumatic experiences, so your body's coping mechanism was to regress

many homes didn't like this, therefore giving you more trauma and it going in a loop until one day...Wilbur adopted you

you regressed at random times when something bad reminded you of your previous homes so Wilbur kept that in mind. you were clinging onto Wilbur as you two watched a movie, Wilbur was softly playing with the ends of your hair