These symptoms are likely related to hypoglycemia. If this is happening consistently, you might be consuming a high-sugar diet that your body is used to getting. It can be rough to manage fasting periods if your intake is a roller coaster of glucose.
Without other information, I’d suggest taking a look at modifying your diet and reducing carb/sugar intake slowly, so that your body is more accustomed to processing foods for glucose rather than having them freely introduced without the effort of processing. You might find fasting is much easier once you’re used to a lower sugar intake.