Oh dear 2Cats ...
I really think it could be developmental.
I don't want to rub it in when you must be feeling awful.
In the last two days, my DD has
(1) turned 14 months
(2) started independently walking for periods rather than just two/three steps then fall down.
(3) after months of teaching her and her not getting it at all, decided to come downstairs on her own on her hands and knees ((I had the shock of my life when I ran to the stairs to see her almost all the way down! She normally sits at the top and cries for my to help her!)
(4) Two teeth that have been bulging in ger gums for ages have come through properly.
And lo and behold, last night we seemed to be back on track with the sleeping!! She had her story and milk, and then I gave her a cuddle and put her down. In the last month or so I have had to sit with her for ages as she had her eagle eye on me to make sure I didn't leave her. Last night, she rolled onto her side away from me and wasn't at all bothered about checking I was there (I stood there gobsmacked, waiting for the wailing!)
She slept through till 8am, in her own cot, just waking once to get her dummy back (after which she went right back off to sleep - whereas in the past month I have had to sit with her for ages again).
It is as if something finally has clicked, and she is now carrying on as before. I can see it in her face - she is chuffed with all her new skills and so bright and sparky too now she has had a couple of nights of decent sleep.
No comfort to you now of course, but I am sure your DD will come through this and it won't be like this for ever.
Have you tried getting your DH to vacate the bed and just having you and DD in bed? You must be knackered and when you are in the middle of a phase like this it is just "whatever works". It really was a classic regression for us - it was like DD was 2 months old again and needing to be with me all the time (and poor old DH in the spare room again!)
When DD wouldn't settle at bedtime I often just lay her on our bed (which she associated with me) until she drifted off. Then I'd go downstairs, and move her into her cot when we went to bed (by which time she would be out for the count).
Sending you courage and hoping that this phase will pass soon.