Congratulations on your pregnancy op.
I think it's disrespectful behaviour on his part. He should respect your space when you ask him to. It's not pleasant to contemplate but it is worth bearing in mind what pp said about pregnancy being a trigger for abusive behaviour.
But putting that aside, and if generally you don't argue, and the rest of your relationship is good, then there needs to be some transparency here and trust here around finances and money, especially as you give the impression that debt is a recurring issue.
You are justifiably anxious. Being worried that your card is about to be declined at the supermarket is no way to live. He's going to be a father and needs to be responsible for the future. He needs to be open and honest, and you in turn need to work on your temper so that he feels able to open up to you.
There are lots of useful articles on the web about how to talk about money within a relationship like this one:
www.moneyhelper.org.uk/en/family-and-care/talk-money/talking-to-your-partner-about-money.
He may be reluctant to talk about money because of the way his parents handled it. Or he may have his self worth tied in to financial success. Either way, tried sensitively, but you do need to get to the truth.
I personally would want to get a very clear handle on how these debts arose and what steps are being taken to clear them. Even if the debts arose before you met, you both need to have a siege mentality about this and do everything you can, work and budget wise, to cut down on spending until the debts are cleared. No holidays, no nights out, no expensive baby equipment. Cut down on bills and extraneous streaming services. Walk instead of using the car. Economise on food bills. For example do you both have a strict budget you work to? Don't be tempted to drift along carrying a parcel of debt with you because it only gets worse that way, not better. And don't be content to live in ignorance and trust that he will deal with it. When you have DC together, your finances will always be inextricably linked together, so it's not a subject you can avoid, especially if you have joint bank accounts and joint rental agreements. And I would be looking to get back to work asap after the baby is born too.
Best of luck 