Depending on where you live a fulltime nursery place for one child is about £1200 / month, a cleaner who does all your household cleaning and laundry would be about (say 6hrs a week at £15/hr) £360/month. So say £1600/month is what it would cost to outsource what you are doing, so he should be transferring you £800/month for his share.
This is assuming he does 50% of childcare in evenings and weekends and shares cooking and all other household and child admin equally too. If he doesn't you need to charge extra for that too. Look into fulltime live in nanny costs, its about £35,000 per year.
At the moment he is having his cake and eating, its exploitative of him and in no way should you consider any more children (or carrying on with the relationship) if he doesnt change his ways.
Although personally, I would be getting back to work asap, and adding to my savings and pension again, as someone who is happy to take advantage of their partner like is, is not a long term bet.
Bottom line, without the security of marriage there is no way you should be doing any of his 50% domestic and childcare for free.