Im Sorry to hear is, no wonder you are in a state of shock. You need to look after yourself and get some RL support from family / friends.
Do you need to contact your GP or CPN?
Will your work colleagues / boss be supportive ? Have you gone into work today?
The things you need to do quickly are -
Finding out when he plans to move out . Sooner rather than later is good as it gives you some space , but of course you can’t insist on this as it’s his home as much as yours. So try to persuade him.
Play detective - get copies / photos / details of any financial assets/ liabilities that belong to both of you. Pay slips, tax returns, business details, savings, pensions , ISAa, stocks and shares , credit cards , insurances, cars, savings. Do this now before he hides anything - remember he’s had time to plan this.
Take half the money out of any joint SAVINGS accounts and move into an account in your own name in a different bank. Do this now in case he takes it all.
You might agree to keep a smaller amount in a joint current account if that is what you use to pay household bills.
If your salary is paid directly into a joint account eg for household bills, change that now. Get it paid into your own name account and transfer what you need to a bill account.
Things you don’t have to do now, but you can take time to get legal advice / financial advice -
Find out the value of all ( I repeat ALL ) matrimonial assets and decide how you are going to divide them. Lots of wives have NO IDEA if their husband has a pension and how much is in in - it’s often a great deal more than the equity in the house. So don’t worry too much yet about how much you would have to pay him for his half of the house as that could be set off against your half of his pension.
I know this may not be the case as you are both young and don’t have children so you may not have sacrificed your career for his.
There are different rules about a short marriage but I see that you have been together for more than 7 years so your solicitor will be able to advise.
Things NOT to do-
Don't beg him to stay.
Don't assume he’s telling you the truth about his reasons for leaving - its highly likely that it’s NOT about your mental health and that he has another woman.
Don’t talk to him about your marriage or try to cry on his shoulder or guilt trip him into staying. He is no longer your friend and you can’t trust him not to use anything you say against you. Be cool and businesslike when you have to deal with him.
Do not have sex with him in an effort to show him what he will be missing / recreate the good times. It won’t work and it will make you feel REALLY shit later.
Don’t get drunk when you are with him in case the above happens.
Don’t try to do this alone - everyone needs support from trusted friends and family - as long as they are yours and not his. Don’t confide in any of his family - no matter how close you are to your MIL / SIL etc.
Dont agree to any division of assets or sign anything without legal advice. If he tells you that he wants to divorce “amicably” without lawyers, just nod/ say you don’t know / are not sure. Then get him to give you details of all his assets and all his proposals in writing (letter or email ) and take them straight to your own solicitor. You don’t have to tell your husband you are doing this - legal advice is confidential.
If your solicitor says “ Yes this is a really fair deal and reasonable deal “ then you will know where you stand, and you can choose how to proceed. But 99.9% of the time , men who say this are trying to rip off their wives, so be prepared.