https://youtu.be/5zddyv1-m7g?si=oGd2ryJbji0qyS1w
Hi Joanne. I can't say when I might have a Lung infection, but have fashioned myself to learn quite a few tricks to keep them at bay. For sure, those Events can be life-changing if ignored or gone unattended.

It's best not to wait if you have definite clues that your condition is in FLARE-UP mode. As to Oxygen saturations and seeking ER medical care - GO if you are really feeling Poorly!! You will (usually) bypass the line IF you have the following COMBINATION: Low O2 readings when going from rest to activity (less than 85%) PLUS Shortness of Breath (SOB, including upper chest breathing only) PLUS a high temperatures AND high Pulse (Heart rate > 120bpm!) Anything less than this combination for a COPD person like me and they will let you watch TV in the waiting room for a bit just to see if it will pass. A positive COVID test result OR very HIGH body temperature will definitely get you in the back room for some blood labs and xRay quickly.

Sometimes low energy could just be de-hydration. Low water saturation could also cause mucus clog to up and it could feel like an infection. Don't be afraid to take a couple Tylenol and a short nap to see if things are more Stable - than NOT. Otherwise, an Urgent Care site or the ER is the only way to know for sure.
be Well.

Thx. Calling a doctor is not possible. And waiting at er can be many hrs , I just don’t have the energy

I would call your doctor. Are you having trouble walking across the room? If so go to the ER.