low saturation level of oxygen - unexplainable

[Daxis1223432]

Hello, i am 55F. I have a low saturation level of oxygen (70%-85%) measured by pulse oximeter in duration for 30 sec to 5 min six times a day - in average.  Other difficulties are: feeling of extreme weakness, feeling of great warmth, tiredness...  It all started month ago with highest temperature ever in my life - 39.3 °C(102.74 F) and after using medications(antipyretics) it fell on 35°C(95 F). Now I have normal body temperature. My otorhinolaryngology report is normal, spirometry is normal, EKG is normal, ultrasound of heart is normal, lung functioning is normal, ABS: pH/7.404; pCO2/1.99* KPa; pO2/19.26* KPa; sO2/98.8%; cHCO3/9.1* mmol/L; BE/ -13.6* . Doctors cannot figure out why do I have low oxygen level and they say it is unprecedented case. I sincerely ask for any advice or shared experience similar to mine.