Could you book into tresillian? I know that for me it was amazing support. Also the tresillian or other parenting help lines are great.
Im reading a book too at the moment that you might find interesting. It talks about babies and what we should do when they just sook!! Sometimes they just want someone close. Do you have a sling you could put baby in and wear around with you? The book is called Heart to Heart PArenting by Robyn Grille.
But definitely a main point of the book is that you need support. So if you need a day, have a day and put DD in daycare. Dont' ever feel you need to justify that. It would mean you are a better mum which is the most important. Especially as you have no one avail to help (not including DH's who are out working most of the time anyway...).
Best wishes and remember "this too shall pass". xoxo