Hello and welcome to wikivorce although I'm sorry you need to be here.
As you have been married for 15 years and co-habited prior to that, the whole of that time is taken into account, which is considered a long marriage. The usual starting point for division of assets in that case is 50/50, but there are a number of factors to be taken into account. For example, providing a home for the children is a major factor in how assets may be divided. The main carer of the children would need a greater share of any assets.
On the face of it, it does seem you have been making major one-sided contributions to the household expenses, family living costs and pension provision.
A good place to start is to assess your finances and make a list of assets, total income and outgoings. Start to get some hard facts down on paper and create a papertrail of payslips, bank statements, receipts for major purchases, etc.
Are there any direct debits? Find all the bills - water, council tax, insurances (house, car), road tax, gas, electric, TV license.
Look at how much is spent on food shopping and petrol. Do you pay childcare fees?
Finally, look at what is coming in...salary. Child Benefit? Tax Credits? Any other benefits?
If your children are to live with you then your husband would be liable to pay
child maintenance. If you are fairly amicable, although it doesn't seem as though you are at the moment, you can agree an amount between yourselves. Otherwise you would have to apply to the Child Maintenance Service for them to calculate the amount he would have to pay, although if he's not intending working...
When you've got all the information together, in order to get an idea of how you might split your finances, it's best to post details of your ages, respective incomes, outgoings, any assets, liabilities, age of children etc and people will try to help you see how things might work out for you.
That's where to start and you will get a lot of help and emotional support on this Forum.