I took Ddog in nearly a year ago, she is from a rescue and had an awful start to her life including being a street dog so never lived in a house before.
She was shut down when I took her in and it's taken lots of baby steps to bring her out of her shell, she is still very nervous in new situations which is a work in progress but generally at home with me she is life and sole and loves her new safe life 
I had to go away for a couple of days 2 months ago so set about finding a registered dog sitter, we did a few meet and greet walks, home visits and all was fine, she stayed in their home and when I picked her up she was full of beans to see me and settled back into our home very easily.
I went away again last weekend and took her to the same sitter, as soon as we pulled up she shrunk to the floor and tried to get under the car and was crying. She used to do this all the time in the beginning and very rarely does now but it's not uncommon so I took some time to reassure her and eventually she let the sitter persuade her inside.
When I collected her she didn't greet me, looked very unhappy and once she did come to me (I sat on the floor) she cried and really lent into me. The sitter said she had been fine but off her food and had taken a dislike to one of the other holiday dogs so they had to be crate separated.
I used a covered crate back in the early days as a safe place (no shut door) just somewhere for her to go which she did very often in those early days. We haven't had a crate in the house for months now she sleeps next to me beside the sofa now
She still isn't her self, very withdrawn and it takes ages of 1:1 to get any level of excitement from her where we had got to the stage where she would show happiness as soon as she saw me.
I'm wondering if she just doesn't enjoy being in a busy environment with other dogs - there were 5 in total, she used to be locked up with 50+ In an unsheltered pen.
I'm due to go on holiday in July for 2 weeks, I'm now dreading it, I hate the thought of setting her backwards when she has done so well.
I'm really not sure what to think?