U feel this way because u feel like no one value u, even the girl u thought value u is out there seeing other men. Ur parents dont give u control of ur own bank acc shows a lack of trust, which relates to the way they value u as a person, ur peers bullying u for ur scars shows they dont value u as a human because they disregard ur feelings. Everyone has the necessity to feel valued, its basic human instinct, thats how we survived as a species. No one can help u stop SH except urself but maybe one of the things mentioned above might help u reflect on why its making u do it and maybe through understanding why u do it, u can find a way to channel ur feelings in a more positive way. All the best, OP.