High Blood Sugar Readings

I was diagnosed 5 years ago as a diabetic. Since then I have been taking medication for my condition. (Metformin and Glucotrol XL) For the most part my blood sugar levels have been around 120 in the mornings and around 95 in the evenings. My diet has been relatively the same throughout the years. 95 % of the time I stay focused on the proper diet for my condition. I did have quadruple bypass surgery in July 2005. My blood pressure and heart are in excellent condition. During the past two weeks my blood sugar readings in the morning are 220 - 230. WHat might be the cause for this.