Your support worker will only feel upset and blame himself if you should go on with this horrible plan. contact suicide hotline in your area immediately. they can help. they have experience and have dealt with worse situations.
i learned to control my rage attacks by punching punching bags, building my rage, and then stopping when the instructor said stop. give it a try, but has to be much more than just one time. it takes practice.
talk to a psychiatrist. sit in a safe place, with someone responsible around, and try to feel how you feel when you're self harming, build it up, and then force yourself to think about being on the beach or someplace peaceful and beautiful. make yourself more calm with every breath you take. you CAN learn to be in control of your emotions. i work on it now every day, and it's working! although slowly and takes much work and effort, but i feel so much clamer and better. try it.
just dont do the last one alone without supervision. you can be in control of your emotions if you want to be. when feeling depressed, angry, afraid, force yourself to concentrate on trees and bushes around you and their beauty and make yourself relax more and more. i do this when my general anxiety gets the best of me, and i swear it's starting to work. just dont expect miracles overnight.
talk to a family member or friend about your problems. surely you have someone in your life, a parent, sibling, friend, lover, someone. if there's no one else, talk to your support worker or the preacher in your community. you'll feel this much better after talking to someone.
this is just a bump in the road, and the road can be beautiful and full of possibilities. dont do something irreversible and will ruin your family's lives. go spend time with your family.