I might suggest, if it's ok, that perhaps the urge to write about your SI is similar to the urge to carry it out: in other words, you're expressing pain. So even if you weren't writing the poems, you might still feel the urge to SI. Do you find writing about the poems helpful? Do you find if you stop yourself from writing about SI, that your negative thoughts go away?
I don't think I'm explaining myself terribly well. But hopefully I've given you some stuff to think about that might help you find the answer you're looking for.