Periodic feeling of heavy breathing.

Since 1 year, I periodically feel that I cannot breath normally. And when it happens I Mostly yawn at times, burping etc. This happenes for a week and then vanishes on its own. December my doc said this can be due to passive/active smoking and I quit since then. Now only smoke I get exposed to is of camphor, agarbatti.. can this also cause such periodic thing? Oxygen saturation is good and nothing in chest xray as well.. is this anxiety? Because when I think about it, it gets worse.. if I'm caught up in any work, activity I don't feel this. No chest pain normally.. can sleep nicely..working out occasinallu..and when I start thinking about it I feel heaviness and feel like taking deep breath. Attached xray taken in Dec. I have no coughing atall.. and no other conditions as such. Please advice