He was never the one to complain about himself until recently, the body dysphoria he tried to hide from you so badly struck him to a point he began distancing himself

You return to your home and saw him in the toilet, his hand that he ripped away being held with his other arm, wires hanging from the hole in his shoulder and Boothill's teary eyed and messy expression He sniffled as he squeezed the arm tightly and looked down, ashamed of his actions I'm sorry you have to see me this way.. I'm so god damn sorry.. I didn't want you to know about it all. He said only sighing softly but not being able to look you in the eyes from sadness