No, you aren't rambling at all. Your concerns seem very on point and real. I would like to do a little research, but I see a pattern here that suggests just what you describe, a sort of oxygen deficit. I have some resources to look at, but I have to say you will need to see a general practitioner, and have some tests.
I don't know if they tested for anemia, but I will say I have had every symptom you describe based on an ideopathic anemia from which I've suffered for 3-4 years. Normally I would try not to use a personal experience to form an answer, but the mental exhaustion combined with everything else just sounds so familiar. The nausea, headache and diareah, and orthostatic hypotension (dizzy when you stand) are all more common to anemia than most are aware. Anemia is a chronic lack of oxygen transport to every muscle and organ, including stomach, brain, intestine etc. I'd always seen anemia as having very specific causes in my patients. Then my Hgb came back below 6 and there was no cause found. This has become a pattern and no cause ever found.
The danger with using my experience and applying it to your symptoms is tunnel vision, and I feel only a Dr. with access to a lab can give you a final answer.
Ginger is a natural anti emetic you can use as a supplement, and for some otc Drammamine helps. There are Anti-emetics the Doctor can prescribe with less sedative effects than Phenergan.
It sounds like a journal of your symptoms that you can present to your Doctor is a good idea, for the purpose of communicating it's seriousness, and organizing some more aggressive testing.
I really hope you are able to find relief soon. I will probably reply or pm you with more information if I find anything else that may help relieve your symptoms. Also, when you have a diagnosis please contact me by pm, and I will be happy to provide information on treatments, etc. (As a follow up-instead of re-posting and paying again)
I hope my answer is helpful. If you have more questions, just ask! I am happy to help. If not, please click "accept" so I may receive credit for my work.
Positive feedback and a bonus is appreciated when you feel I've earned it. Thank you, Christy