I'm so sorry hun! I know exactly how u feel unfortunately. At the moment you have to just remind yourself that they are just thoughts of self harm (I presume from what you've said you haven't taken action?) Remind yourself that thoughts cannot harm you! Try and distract yourself as much as you can - which I know doing anything can be hard so it's even as little as being mindful of what's around you- labelling things in the room etc, or meditation - anything to distract you away from those thoughts!
I also agree that you could do with finding some sort of therapist to help you through it all!

Sending massive hugs to you! xxx