Hello jess I’m really sorry that this has happened to you. I am in a similar situation so understand how hard it is and how at first you are acting in shock.
The best thing you can do is get some initial legal advice - it might be tricky pre Christmas but at least get an appointment in for the New Year. Most solicitors will do an initial consultation - this helps you understand the situation and, if they are good, will also give you some steps to take.
Legally he is entitled to be in the house - so you should do anything like change the locks. The starting assumption on divorce is 50/50 for both the assets and the children. Each particular situation is then looked at however and the needs of each partner and the children are assessed.
Please try not to panic as all this will take time to sort through.
The most important thing I did was tell a couple of close friends. I also told my boss at work. This has helped me enormously. If there is someone you can confide in then please do try and get some support. I have also posted here a couple of times when very down and have received amazing support. Others kindness has really touched me and given me hope.
What you do next is really somewhat dependant on how you are and what you are thinking about the future. You are probably in shock at the moment. My husband wants to end our marriage so I know that is what I am looking at ( as opposed to say trying to save the marriage)
I found it helpful to make a practical list and try and work through it. So I began to get the best handle I could on the household expenses, incomes, savings, pensions etc - for me this is partly with the aim of seeing if I could stay in the marital home for a while with him renting. I got legal advice. I began to take copies of key documents. It may be too early for you to do this but I changed my will and my elections at work for my pensions so it went to my DCs. I saw a mortgage adviser just to work out how much I could potentially get, then looked at local prices to understand what I was facing (I know we will have to sell the house). I’ve also looked into childcare as I won’t be able to continue my current arrangement long term.
One piece of advice I got which I have found helpful is try and identify the key things that are important to you. Be prepared you may not get them and will have to flex but have in mind what is important to you.
Good luck and
to you. Wishing you lots of strength.