Oh nic, from what you've been going through your being a great mum. You love and nurture your little ivy. Being a mum is a really tough gig and I'm the same, not reacting to how I thought I would.
Like km mentioned, totally reconnend Save our Sleep, it's a great book and really helped me when I was at a loss about 3 weeks ago. If you can't get the book, go one get website and you can download parts of it.
Do you have some family support around that can take ivy for a couple of hours so you can have some "me" time? Also try calling tricilian, the ladies there I found really helpful. a sleep school maybe helpful?
Being a mum is super tough, especially when you don't get a break and it's so mentally exhausting. As well as physically, I was only in tears about this to DH the other night, so know your not alone *hugs*