My husband got covid positive from 17th may 2021 (its been 3 and half months till today). 24th May he took ct scan had 25% lung involvement 17/25. Was on oxygen support for a month and got discharged on 22nd June 2021 (its been 2 and half month till today). His oxygen level is 98-99% in normal position. When he doing brisk walk or climbing stairs faster. His breathing is faster for 2 mins and comes to normal and his oxygen saturation levels also starts with 89-93% fluctuating for few seconds and ends with 99% for a long time. Is this normal?. He is having occasional dry cough 2 to 3 times in a day that time he is having very mild pain in his chest. His respiratory rate is 20-22 bpm. Should I need to worry