Fatigue from workouts

Started CF 2 weeks ago. Going for 3 classes per week. I have not exercised this much in 3 years because of pregnancy and child birth. It's been 18 months since the delivery so I started with CF now.

During the class, I struggle to complete the workout, I go breathless few minutes and my heart rate goes up to peak (192bpm, my age is 32) for 10 minutes.

After workout I feel fatigued and lazy throughout the day. I don't want to do anything else just want to be on the couch. My brain seems fogged and can't concentrate on work much.

I used to do some kind of exercise before pregnancy and never felt this way. But that was not CF.

Is it common to feel this way? What do you all do or eat to make your body recover from each session?

I'm starting to feel CF might be a little too much for me and worries me it may hurt my heart. My family has heart problems but not from CF. The opposite, lack of exercise. May be I do some other sort of workout?

TIA!