Eating enough/losing muscle

I have been on 2.125mg of tirzepatide for about 4 weeks and I have been feeling so nauseous and low appetite. Yesterday, I did a long walk and a heated sculpt class and realized after dinner, I had barely eaten 900 calories for the day. I should've noticed sooner because during the class I felt so weak! I slowly made myself eat some greek yogurt to round up to 1,100. It kind of made me worry and I'm curious does anyone else track calories to make sure they're getting enough calories and protein at least? Is 1,100 calories too low for a day? I can barely finish a full meal but I don't want to be too weak to enjoy a workout class or lose muscle.