Basically yes - you have a financial penalty for being a woman and having a child and not choosing to walk away.
It is absolutely crap, CMS rates are a joke, men are (often) bastards and yes the cost of raising your child will fall largely to you for the next 20 odd years.
It is true that many, many mothers deal with this without having two decent salaries as a starting point - and I can’t begin to describe how stressful and unpleasant that is - so in some ways you are in a fortunate position compared to others. But the position is still crap and I really sympathise if you didn’t have any idea of ow this would play out financially, you must be having a complete shock.
I’d only say, for your child’s sake, try not to make your life and your/his relationship with his dad (if one develops) about money - it’s a toxic dynamic for you both to live with. It’s bloody difficult, but it really is better for everyone if you can separate these issues.
It is sadly true that you may be marginally better off financially In the short term if you drop some hours and pick up UC input, especially in nursery fees (you can earn a decent salary and still get this). At the very least make sure you’re doing the tax free childcare thing. But with the long term in mind I would do everything I could to maintain and even increase your salary, even though it means taking a financial hit until you’re entitled to some free hours etc, get to primary school etc.
Be mindful of the fact that a secure job, and any job with some flexibility in hours/working patterns, where you are trusted and there’s some give and take etc is gold dust when you are in this position. Also be mindful that, while nursery is a massive cost, children also do get expensive on other fronts as they grow and you can’t get much help with utilities/food/rent or mortgage/activities/clothes/uniform/shoes/
birthdays/ christmases/presents at birthday parties etc etc So if taking less hours now is possible then great, but don’t get trapped on a low income if you aren’t confident you can quickly bounce back in your career once free nursery hours/primary school start, or the pain will just carry on even longer.
Welcome to single parenthood. It sucks.