Following a bypass surgery, pain can be of two kinds. One is pain from the wounds and muscle and bones which are cut during the surgery and this pain and discomfort can last up to 3-6 months and certain people even complaint of tightness even beyond this period. The second kind of pain is the typical anginal pain which can return after bypass surgery in certain people where the smaller arteries are blocked or where the bypass operation itself may have some blockages coming up.
Its extremely difficult to treat a specific problem through email and I think you would have to contact your doctor only in this matter.