Hey Myjoy!!
I had shoulder surgery about 2 years ago. Torn rotator cuff, bursitis, frozen shoulder, yadda yadda.. anyway, I only needed one MRI and one X ray. Maybe the tech that did your MRI a couple of years ago didn't do such a good job and your doc would like to have another done for that reason .. or since then maybe some scar tissue had developed.
Shoulder pain is really a bummer. I can totally relate. Did your doc send you for PT for your shoulder? PT helped me but it wasn't enough. I did the PT thing for about 3 months, before the surgery and then I went back for a few visits after. The surgery really wasn't that big a deal compared to the pain I was in before. Now it's the best joint in my body!! It was totally worth it!!
Good luck.. and I hope you get some answers.
Warm hugs,