I have banged my head against walls as a kid as a way of coping with mental and physical abuse from my mother.
I tried to strangle myself in my preteens, but didn't follow through.
Later I tried to take pills.
I cut myself a couple of times in my teens, but mostly I used binging and purging to self harm.
In extreme times, I would break things, like umbrellas or baseball bats against trees, walls, pavements.
Or I would put my fist through walls.
I also punch myself in the face or head (temple or jaw usually) when I am extremely upset/angry/stressed.
When I am really stressed and feel I can't go on, I obsess about suicide. Strangulation, hanging, cutting my throat, or my belly (harikari), slitting my wrists (the permanent way, not the cry for help way) and I have come close to all of them but not followed through.
I keep going back for more therapy. It helps get through a rough episode but the depression/desperation comes back.
I'm a grown woman and should know better, but it's a coping mechanism I've carried with me through the years. I've never told anybody about it. I am now.
They say people who self harm do it for relief from painful emotions.
I have been diagnosed with borderline personality disorder as I find it so hard to manage my emotions and moods and impulses and find it hard to hold down jobs or relationships.
It's pretty crippling.
There is help though. See a therapist that specialises in post traumatic stress disorder. You don't harm yourself unless you've experienced trauma, usually as a young kid.
It's really more common than you think.