There can be different pain associated with CAB. Incisional pain subsides gradually over the first month post-surgery. Many patients report a sensation of numbness on the left side of their chest which results from the dissection of the internal mammary artery. Some patients can barely wear a shirt for a few weeks following their surgery due to a hyperesthesia over their sternal skin. Fortunately, all these malaises subside within 1 or 2 months post surgery.
Your pain only when sleeping on your side indicates there may be inflammation of the sternum (rib cage is wired together at the sternum). There could be sternum dehisence....partial or complete separation. You should contact you doctor to rule out these conditions. Your condtion my be due to slow healing, ....12 weeks is longer than usual.