What Causes Sore In Arm Pits And Arms?

I'm going back and forth from Dexilant and Omniprazole due to having Barrett's last year. (no longer have it, but still take medication) I only do Zumba on Wednesday nights, so not a lot of exercise other than walking. My problem is I have very sore armpits and arms both sides. I've had a mammogram this year and everything was fine, however still concerned. What could this be from? Oh...I'm 45 years old as well.