Help plz

Hello I am currently 24 weeks pregnant with my second child. My fasting numbers are very high 120 and above and my doctor recommended I started taking insulin. But the also wants me to take metformin as well. I don’t see them until another week, and I asked them to help explain what metformin was and the side effects and I got no answer. They just said I need to take both…. Does anyone have any experience with taking both of these or just metformin? Thanks in advance for all your help!