New to COPD

Hello, I never smoke, was around smokers most of my life, parents, husband, etc.
I get sick several times a year, I guess that has put scars on my lungs.
I was recently told by a lung doctor I had COPD.
I hear about COPD thru TV etc.  But what is it really?  I started to research on my own.
That is how I am here looking too.
I am concern that I am on Oxygen right off, and using 2 lt mostly was told to use 3 lt when moving around.
But I been afaird to use that 3.  But last night I was having some trouble catching my breath and tired, so my husband  put it up to 3lt.  I just read about someone else using higher number although.

I am under impression I am using Oxygen when a lot of people are telling me they didn't have too?
I don't understand why I have too, but that was order for me by my lung doctor.
I am going to get a 2nd opion about this COPD mostly because I can't believe I have this.
And other people have told me they have copd and had it for years and so far are not on Oxygen?

So I guess I'm asking........what tells a lung doctor by a test with a spirtmetor (breath in it) and xrays that you need oxygen?  I can't get in to see this doctor until next month

So has anyone else have this happen?
The doctor said it was the enviorment, maybe I had valley fever wihtout knowing it, and the type of work I expose too.
Thank you for any information.