Either I walked into a wall or threw a cover on/off, but my left upper arm aches and no longer goes as far up behind my back as my right arm, not even up to my waist. Where do I start, because it has not improved by my doing nothing for 2 months?

you could probably start by going to your regular doctor and he will probably refer you to a physical therapist.

I would go your regular doctor first and see what he/she says. A lot of insurances you have to get approval before going to see a specialist. If your insurance doesn't require this I would call a orthopedist. A ortho doctor specializes in the area of bones and joints. Sometimes it takes a while to get in to one. So you might need to go see your regular doctor and he can do xrays and go from their and he could refer you to someone if you do not know any one. I know some one who hurt their upper arm/shoulder area and put off going to the doctor and when they finally went her shoulder was mess up pretty bad. They said she had frozen shoulder. She could not move her arm above her shoulder. You need more than physical therapy you need to find out why and go from their.
a nurse

See your primary doctor first. He she may refer you to an orthopedist or to a physical therapist. Most insurance will cover both; however, you may be required to get a referral for an orthopedist. And some state regulations require that you get a referral before seeing a physical therapist.