Constant tightness in chest

I was just curious of how long you've dealt with feeling like your short of breath?
To me it just feels like tightness in chest like I'm not breathing as much as I should? I honestly don't know how to fully explain it. I'll check my levels and I'm usually at 98-99% so I'm getting air! But wtf! It freaks me out that this has been going on and off for so long.