My 7yo DS has dxes of SPD, anxiety, and ASD with a PDA profile. His anxiety has always been very bad, particular over separation. He has never settled easily and has always had cuddles to sleep at night, from either DH or me (or will settle with either of his grandmothers but only if neither DH nor I are around). We've had some success with a weighted blanket which means the person settling him can just lie next to him rather than having to drape their arms and legs over him which was previously the case!
He's currently going through a terrible phase with settling to sleep. He cries and/or shouts and/or screams for prolonged periods (up to a couple of hours), says that he hates himself, is bad/naughty/rubbish, that it's all too hard, that he doesn't know what to do, that he wants to calm down but can't, and that he wants to go to sleep but can't. He hits himself with his fists and/or his pillow, throws things in his room, and curls up in a tiny ball in the corner of his bed, rocking and sobbing.
I think this phase has been triggered by his growing awareness that other children don't have to be cuddled to sleep at night - a couple of times, he has asked to be left alone but then ended up in a terrible state, obviously desperate to be comforted but not wanting to admit it. He is also going through a generally more anxious phase at school, worrying about questions from other children about why he is doing xyz differently from them. The phase has got much worse in the last couple of weeks after DH and I went away for a couple of nights (because we were at breaking point!) and left him with his grandma.
We saw the paed at the CDC last week and I mentioned this problem. She said she would send us a sleep diary and a "sleep pack" (presumably with some helpful 
suggestions for settling) and that we could discuss melatonin at a later date if all else failed. She is also re-referring him to CAMHS, who previously discharged him, but I'm not holding out much hope that they will be able to help.
We've now got ourselves into a situation where we have no routine at all at bedtime as we're so desperate to do anything we can just to get him to sleep. We've had some success with the Dawn Huebner books on anxiety and temper, so I got the "dread your bed" one, but tbh the suggestions seemed laughable in our current situation!
Sorry this has been so long. DH and I are exhausted and near breaking point. Any advice or empathy would be really welcomed!