Breakup depression

My boyfriend of 2 years cheated on me and then left coz he thought it would be easier about 2 months ago. I miss him so god damn much, but I know I can't be with that type of toxic person (that and he would never take me back). My depression has once again hit an all time low with self harm thoughts and I haven't slept properly in weeks. Is there anything I can do to get over this pain or at lest regain proper sleep. I have attempted to move on with others, but it's not fair on them and only works as a short term distraction. Please I just need some advice or support xx