If the mortgage is not paid, his credit rating will be affected. Is he aware of this? A bad credit rating will affect his ability to get a mortgage elsewhere and have other repercussions. It doesn’t matter if he’s not living in the house, he’s still legally liable for the mortgage payments.
The position is that you are “jointly and severally” responsible for the mortgage. That means the bank can hold you responsible for the whole amount and they can also hold him responsible for the whole amount. When push comes to shove they tend to go after the one who has the money (or other assets). First, immediately notify them of the change in situation and request whatever concession they are willing to provide – a payment holiday, a temporary interest-only arrangement, whatever.
The fact that you are not married does put you at a disadvantage. There are various changes you need to make to your finances at this time. You can notify the council that there’s only one adult in the house and that’ll get you a concession on council tax. You can ensure child benefits and and child tax credit elements come to you. You can claim maintenance on him for the child that is his.
You need to speak with a lawyer or at least one of the free services available online.
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