Heading back to work

Am looking for anyone who has been in a similar situation or has any information that they could give me.
After 4 years in an emotional and financially abuse relationship I chose to get out. I've moved back home with my parents so that I could better look after baby.
I've been at my job for 5 years on a 40 hour contract. My parental leave has nearly finished and I went down to see what I could do with my hours. I work 8pm to 4.30am (nightfill) and have explained to them its no longer possible for me to do those hours as I have no one to look after baby. My parents were happy to look after baby until 1am, but my job have come back and said to me that I have to finish at 4.30am they won't change their minds on it.
What can I do, it doesn't leave me with a lot of options and I want to keep working.
Can anyone help??