So this phenomenon is recent. ~1.5 years. Coincidentally. Till 3 years ago I used to be a long distance runner (and daily 6-10km on an average) and used to trek and swim regularly. That gradually stopped to a halt. But then I had added daily sports to my routine.

I will try HEPA filter in my bedroom (can't do it for the entire house - it's quite big, open, and a shared apartment and not designed in that way really)