Sorry OP that he's been a twat.
Ultimately he does co-own the house. He can't force you to leave, and vice versa, except by "forcing" a sale.
You need to act carefully here because legally forcing a sale will cost much more than if you can "persuade" him to move out of his own accord.
So, do not:
*Act aggressively or threateningly toward him - he could call the police and potentially you could be removed from the house.
*Lock him out - he has a legal right to reside there and if you change the locks he can ask police to assist him in gaining entry. Costing you an emergency locksmith callout.
*Tell his work - you'll look like "the crazy ex" and realistically unless he's shit at his job and are looking for an excuse to sack him, they won't care. New woman has only just joined so they're going to be more concerned about retaining him than someone still working their probation. Also, he hasn't done anything which would constitute grounds for dismissal.
*Invite random men round to "rub it in his face" or try to make him jealous. Totally unfair on said randoms and you risk antagonising him to the point where he'll deliberately dig his heels in on leaving the house.
Do:
*Immediately stop any household chores you do which aren't for your sole benefit. Cook, clean and launder only for yourself. If he says "I'm getting a takeout, want some?" you say "no thanks" and get your own.
*Stop sleeping in the same bed (if you still are). Separate your things so you don't have to go into "his" room to get dressed, and vice versa.
*Invite friends and family round to socialise, and feel free to monopolise the living room, kitchen, etc.
*Don't facilitate his life in any way - for example if you normally remind him about mothers day etc, stop doing it. Don't give him a lift anywhere. Don't lend him money.
*Carry on your life as calmly and sensibly as you can. Don't let him see you crying or raging. Be like a swan - all beautiful and serene on the surface, legs thrashing away like mad below the surface!
*See a solicitor so you know exactly what the options are if he won't play ball with you buying him out. This way, when he starts trying to bullshit you with "Actually by law you have to leave because I said so" you can tell him to bugger off.
*Tell everyone and anyone you like what is happening. Don't assassinate his character to his family but be factual. Save your hurt feelings and anger for your friends who will have your back.
Hope some of this helps. MN is a wonderful resource but you also need real life, practical support. You will be okay 