over working fiancé?

So I'm currently 11 weeks pregnant and I have the most amazing fiancé. On top of working 12 hour days and running his business he literally does all the chores in the house. Dishes, cleaning, laundry. He doesn't want me to lift a finger while I'm pregnant. And I get that but I can tell he is overwhelmed sometimes. I try to help but he gets upset. I'm afraid that he will keep this up and maybe snap one day from working so much. Any advice on how to convince him to let me help out?