In April to Aug2025, I had recurrent severe colds/URIs with tonsillitis requiring multiple courses of antibiotics. It cleared in August. In September 2025, I experienced severe lightheadedness for the first time, one day before my period. Since then, similar episodes have recurred around my periods, but also at other times, especially with sleep deprivation, around meals, and particularly while sitting. From Oct 2025–Mar 2026, GPs repeatedly prescribed Vertin (betahistine), which did not help. In April 2026, I was diagnosed with sinus tachycardia; my lightheadedness became much more frequent during a period of severe burnout. A 24-hour Holter showed an average HR of 94 bpm, maximum 153 and minimum 43, including elevated rates at rest. Symptoms became less frequent in May–July. In August 2026, I developed another cold, had my period, and developed jock itch requiring ~2 weeks of treatment. After this illness, the lightheadedness increased again and now occurs during multiple cycle phase