Don't know if anyone can help me

Me n my partner now ex went on a joint claim I have 2 children and heavily pregnant 🤰🏼 we had a payment Wednesday but iv checked my account and looks like his transfer himself what was left the money that was left was my child tax credit for me to do stuff with my kids over the Easter holiday n see us though the month what can I do to get the money back after the bank holiday I'll be calling universal credit to go back to being single but will they help me out even tho iv already had payment n a budgeting advance any advice could really help thank u