Chest Rib pain comes and goes, worse sitting

So for a couple months now i've had this nagging pain/stitch, seems just to the right of my upper chest or sternum. Kind of shoots sometimes to the bottom of the left ribs too.  Started feeling like heartburn at times going down to my upper stomach. Got a check up, ekg  is very good, blood test all normal except high blood sugar count. GP put me on 2 meds to lower the count. Its working and for next 10 days is having me double it up to get it down to 140 range.  He put me on prilosec too. Got a egd and colonoscapy schedude in a couple weeks too.  I should learn more after that. My GP told me to lay off excerise or prolonged activities for a couple weeks, just get about 10 minues of easy walking activity in.    But my question now is I seem to function much better when i'm walking, doing things, not sitting or lying down.   I feel better when i'm out and about as well as when i was on the eliptical felt okay too. How come?  Also, could there be a relationship between the high blood sugar levels and these chest/rib pains?  Possible GERD the cause? Thanks. Bill.