Weak Diaphragm. Advice?

Hello all, thanks in advance for your time.

I'm trying to figure out what's going on with my breathing. The thing that's most obvious is that I am frequently using extra effort to breathe by way of having to flare my nostrils or suck really deep through them, and sometimes I even feel my neck and shoulders kicking in to get a good breath. Additionally I've noticed my abdomen feeling very weak and low often times. After doing a little research I'm wondering if I've just allowed my diaphragm to get very weak due to a long lack of activity during the lockdown.

I'm also experiencing a lot of weakness and dizziness in the mornings that last quite a while, and my breathing is uncomfortable and feels forced as I try to go to sleep as well.

First question I guess I'm asking is if a misbehaving diaphragm alone counts as COPD. I fortunately have not experienced coughing or wheezing or any kind of substance build-up in the lungs. But the diaphragmal and muscular breathing behavior my body's been having is very difficult to deal with and I only recently am aggressively doing abdominal breathing exercises in hopes to retrain my body. Is this something that you guys would recommend?

My other question is if any of you guys have experienced sleep difficulties and difficulty operating during the day due to COPD issues. I was suspicious it could be some sort of sleep apnea but but that's unlikely as I am young, slim and don't snore.

Any insight and encouragement I would be so grateful for. Feel free to let me know some of the basic things I can start doing to improve my quality of life which has been lowered a bit lately. Sleeping and breathing should come automatically and feeling like you have to fight for it and are being robbed of it is quite despiriting.

Thanks so much.