My spo2 reading on my garmin vivoactive 4 is reading 90 today from normal reading of 95 and above. it started decreasing since monday. is this normal and im feeling weaker.

Talk to your Dr.: SpO2 readings on non oximeters can vary in accuracy +/- 4 points. If you are feeling weaker and your SpO2 readings are decreasing, it could mean that your respiratory efforts are being compromised. Talk to your Dr and determine if you should be seen in their office or at an urgent care. If you have other symptoms: fever/chills, shortness of breath, cough, persistent chest pain, go to the ER.