I'm extremely fatigued, my heart is racing, I feel weak
I would explain as follows:
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I passed carefully through your concern and would like to explain that your clinical symptomatology is suggestive of an anxiety disorder.
You feel exhausted because of uncontrolled increased of stress, leading to persistently elevated catecholamines in circulation.
This in turn explains the racing heart and elevated blood pressure.
Coming to this point, the first thing to do is avoiding any stressful stimuli and shortening your work period. Several recreational activities are advisable (walking in a park, cycling, reading, etc.)
I would not prefer taking medications, but If it were an option a careful medical checkup is recommended before.
Hope you will find this answer helpful!