Sorry you are having these thoughts. I have similar thoughts. PLEASE dont act on them tho - it doesnt help, as others have said, and can only make things worse.
When I feel like this, i try to distract myself in any way i can ie talking about nonsense with friends, reading posts on PC, drawing, writing, painting my nails, or drawing/writing on my arms with pens. It helps, cutting doesnt.
Try to believe that you are a good person who doesnt deserve to hurt themselves. I believe that about you because no-one 'deserves' to SI
Take care

*Willow*