Are you able to work?
If you are, make steps to be employable again - training, volunteering, part time work...
Because there's a fair chance that one day this is going to blow.
For me, I knew I wanted to leave when my child was 4 months old - I had said fairly strong (but not conclusive) evidence that my XH was using prostitutes
I knew then that it was when, not with.
I stuck it out for four sodding years 
Separate rooms, no sex, living largely separate lives.
For my child to have both parents together. Because my work shifts and travel seemed hard to manage separated. Because I couldn't bear to give up time with my child. Because I didn't want him meeting someone else whilst my child was so young she might have thought she was another mummy. Because I ended all physical interaction with him so didn't feel forced to end it to avoid that. Because I was on mat leave and my baby woke 8x a night still at 11 months and I was too tired to take any decisions. Because change is always harder than coasting along.
The only thing not a factor was finances as I've always worked and we had savings.
So... Four fucking years.
Then it got too much.
- I hated him
- I wanted sex
- I didn't want an affair (funny, my morality compared to his!)
- I didn't realise it then but I wanted to be loved and cared for and have an emotional connection with someone good
- I had a sudden moment when a friend was made redundant when I realised that my escape plan relied on me getting a mortgage (easy then) and if I got made redundant my back up escape plan was fucked!
- and the big one... I suddenly realised that at 4 years old, my child had never seen her parents kiss, touch, hold hands, hug, laugh together, smile together. I thought "if she accepts a marriage like this it will be YOUR FAULT". I sobbed for hours. And a week later cut loose from the arsehole.
I didn't realise how stressful it had been, in my loveless marriage until I was out of it. Don't underestimate that.
Now... I have lots of sex with a man who I'm crazy about and who thinks I'm amazing and we're getting married. My 7yo giggles "germs!" at us kissing, and sees what a loved up couple who care about each other look like. Not just the kissing - the little looks, doing things for each other, the laughter.
My best friend said: you've given that arsehole your 30s, don't give him your 40s too.
I'm happy, as is my daughter - with two parents that love her, and two step parents to be that think she's great and assorted step siblings too.
Now OK yours isn't cheating. But if you live separate lives but for the children one or both of you is going to want eventually.
When they're 18? Why would he stay with you then? Don't wait another 9 years to suddenly have to sort out your finances on your own going forward, when you won't even get a greater share as main carer (if you even would be main carer now)
Stay if you want, but cover your back: work.