Hi newmum84
I’ve been through something very similar with my ex, who has been actively damaging to my mental health and ability to parent since day one. As our situation is still really difficult, I dont have much advice for you, but wanted to raise a fist in solidarity and tell you that from my point of view you have done the right thing. You need head space to be able to think clearly and get on with the task at hand. You have loads on your plate right now trying to raise a little human, as well as keeping yourself afloat. You do not need someone else dragging you down. So well done, let yourself breathe.
As for what’s next, you now have the opportunity to build up your support network, unencumbered by someone who would otherwise stand in your way. Your baby is still really portable, so go out and meet people as much as possible. Do things you enjoy. Reach out when you need support. Look forward to the day you can get a friend to give you a night off. And enjoy the delicious intensity of an uninterrupted relationship with your baby.