Financial support

So my BD left me while I was pregnant. And I was getting CMS from him but he’s gone on the sick so I’m getting nothing atm. And I’ve got my mortgage to pay and I’m only working pt and paying for nursery. UC are paying me something but they’re deducting me as they do anything over £675 you earn. Which is ridiculous how are we meant to live on that with mortgage payments and living?! What help then take it back away from me? Any advice anyone in a similar situation? Xx