Brain fog, exhaustion and trouble with memory and calculations together usually point to a correctable cause rather than anything serious at your age, most often a
vitamin deficiency, anaemia,
thyroid imbalance, poor sleep, or anxiety itself feeding the symptoms. The unsteadiness while walking is worth checking properly rather than assuming it shares the same cause.
Next Steps
Get the tests you listed done,
vitamin B12, D3, CBC,
thyroid profile and
electrolytes, plus a basic blood
sugar check. See a general physician with the results and mention the anxiety and balance issue specifically so they can examine you properly.
Health Tips
If the unsteadiness is getting worse, or you have slurred speech, blurred vision or weakness on one side, get seen urgently.