Dear OP,
I am a long time lurker but hardly ever post, but had to reply when I read your thread.
I am going through similar feelings right now, as my mother died in January, after a long illness which resulted in extreme weight loss, which was very hard to witness. By the end she resembled a victim from a WW2 concentration camp. 
I'm haunted by what I witnessed and have spent many hours berating myself and wondering what I could/should have done differently for her. I think we both need to tell ourselves that we did our best to support our mothers through their difficult final journeys, and try not to punish ourselves for things we had no control over.
As for your "friends" telling you that you should be over it by now - I'm speechless at their clueless attitude and so angry on your behalf. A few weeks is no time at all to recover from such a loss, especially considering the distressing circumstances of your mother's final days. It sounds like you are going through something akin to PTSD as well as all the usual side of bereavement, so it will be hard to work through your grief. I hope the counsellor will help.
Your ex partner's behaviour sounds vile. It's true that it can be hard being around someone who is tearful and grief stricken but that is what a decent partner/friend does, they stick by you in the tough times. I'm aghast that your "friends" seem to be siding with your ex partner, but they all seem to be cut from the same poor quality cloth, so maybe it's better to find new friends, when the time is right.
I've also been let down by a "friend" who showed no empathy or support after my mother's death. I'm afraid I can't forgive her and want nothing to do with her, now I've realised that she's so thoughtless. My DH has been great, so I'm lucky there, but as the months go by I wonder if I should try counselling, as it all falls on DHs shoulders.
On the sleep issue, I've suffered long term insomnia for years and the grief has worsened it. I find that the radio helps, something like R4, a play or talk show. I sit there with the lights out, with my eyes shut, and wait until I feel really tired before going going to bed.
It's tough OP but you're not alone.