Hey MsTeecher,
Thanks for all the good advice. The truth is that I never saw myself as a runner. It's always been uncomfortable for me, probably because of my stature (tall, large frame, lots of muscle, and at times lots of fat - though not lately!

). What I can tell you is that I'm not a "butterfly crusher" nor are my arms particularly stiff. They swing from the shoulder, although I'm not 100% sure that they don't cross the midline. I'm going to say that they don't, but tomorrow I will double check.
Also, in regards to running faster than I should, sometimes I find that if I run SLOWER it's more uncomfortable. The truth is that I started with the speed at 9.0 on the treadmill and have been upping it gradually over the last few weeks. I now feel comfortable at about 9.7.
It's just so uncomfortable for me. Sometimes I find that I have to stop and walk for a minute or so, not because of being tired or out of breath, but because my arms are so tired. It's so frustrating!
I will definitely get back to you with the arms-crossing-the-midline thing tomorrow.