Turn litters up and down

good morning, I’ve just been out of the hospital for four weeks with about a pneumonia for 15 days. So I came home on 5 L of oxygen when I was on 2 L. Now I find myself where I can wean myself down to four when I was with physical therapy, but there’s times when I feel like I need to move back up to five. Is this normal to go up and down they say that if you are exerting to give yourself a little more air to breathe. I also noticed that on the little breathing things they give you in the hospital, the VPAP that I think I blowed it maybe too hard I don’t know or cough too hard so now my ribs hurt just on one side could that be from coughing too hard and what can I do? Want to be in good shape starting my pulmonary rehab this week I can’t wait and sure. Hope it helps.

Thanks

G-Ann