Years ago I posted in here because I felt like abandoning my children and disappearing into the ether. I felt nothing except a desire to leave everyone and everything.
Today, I am doing a lot better. I am not going to say everything is great and perfect; it's not and I think I will always live with a degree of mental illness, but I'm stable, I'm working FT in a great job, the children are much older and largely independent which means I have time to do things I like. It's an easier life.
I imagine you feel overwhelmed by your situation at times and I wish I could tell you something to make it better but ultimately it's up to you.
Daily yoga and meditation will be hugely beneficial and it's something you can do without cost as there are lots of free programs online. You will have to take the first step of making time for yourself to do it, but I guarantee that if you invest 15mins a day in this, that it will help your mood.
Some people swear by a gratitude diary. I don't do it myself but possibly it is something that may be helpful. I don't mean to suggest that you should be grateful for having what is essentially a very difficult life, but sometimes we can ease our anxiety by reframing things a little. Physically writing down 2 things a day that you're grateful for, even a giggle from your baby, will help your mood.
In practical terms, all I can suggest is seeking advice, perhaps through a CAB to ensure you are receiving any benefits and support that you're entitled to; approaching a food bank for assistance, and joining a social group, perhaps for other mothers of young children, that gives you the social connection you need. It needn't be a cost. There must be other lone parents who are in similar situations?
I'm sorry that things are so challenging for you. It's not how it's meant to be at all. I think that if you can focus on a day at a time, the days will become weeks and months, and gradually the challenges will ease. Can you visualise what you might be able to achieve in say 5yrs? Maybe working 25hrs (for money and social reasons) and having time with friends, as well as precious time with your then 6yo?