Hi Vendyn, welcome
Im sorry you are in this predicament.
Firstly, I'm confused. You I presume is a male as your partner is on mayernity leave. Yet you mention "to get back at him"???
Anyway, I feel that your now ex partner didnt waste time dating. This could be that she is making you jealous to spark something between you. Did the dating process take such little time?.
I think you are now pahing the price for not attending to her needs. Thats done now but seriously, even if you dont get back together flowers, a nice dinner etc could change her thoughts.
She being the mother of your child it is most important you remain on that friend to friend level.
Many years ago I purchased a cheap caravan and lived in a caravan park for several months. It was ok to have my kids there to. But it is only good for a temporary fix. Or shared rent.
I cant see you being able to remain under one roof. What happens if she wants to bring her date home?. Also would it be appropriate for her to spend any unnecessary monies while you are trying to keep financially afloat?
In the meantime, visit your GP for a chat. Its wise to look after yourself, for the benegit of you and your baby.