Your debts will be separarate even if you are married.
However, if you are married, the bank may well ask him for your financial details if he is trying to negotiate a deal with them. He is under no obligation to give these details, but then they are not under any obligation to offer him a deal.
However, if he lives with you, he may develop a claim to your home, as it's the family home. He could claim that he helped you pay the mortgage. However, the bank would not be able to claim that he has a right to a share in your home.
You probably need to ask yourselves whether you can afford to have a child at this stage. You might try to resolve the financial issues first.
Your boyfriend should look at the options under the Personal Insolvency Act.