Is this cording?

It does sound like cording. When you extend your arm straight up, do you feel cordlike structures standing out?  Do your stretches gently and hold each. Hold your arm up (like walking up the wall and massage under your arm or do this under the shower. I should say though that I was shown how to do this by a lymphoedema physio.  My best suggestion is to make a appointment with someone like this as soon as you can - I have a combination of laser therapy and massage, and sometimes a sucky thing called physio touch.