What Could Be Causing Chest Pain, Upper Rib Discomfort, And Shortness Of Breath 3 Years After CABG?

hello. 3 years ago I had CABG surgery all 4 blocked. recently Ive had issues with physical pain in chest area behind surgery site and upper rib cage. Also onset shortness of breath. After I eat I feel over full in that area when I dont really eat much. I had an xray at the end of January and all was good. Heart was checked in december and all was good. What could be causing my pain and shortness of breath? Thanks