The nagging thought in my mind: "When did this bruise appear?" You're now a little over 2 weeks post-op, while it's normal for bruising to take its sweet time in resolving and everyone heals at their own pace, I would expect any bruising incurred on your date of surgery to be fading (or at least changing colors).
Other thoughts:
You were likely given anti-coagulants immediately post-op. Do you remember any shots in your belly? If so, these could have caused some additional bruising on your belly.
Has it gotten worse in the last week?
Is it painful or just unsightly?
Regardless of my thoughts and questions, my advice to you is to contact your doctor's office and let them know. If it's nothing, then at least you've gained the peace of mind by being told by the doctor it's normal and/or nothing to worry about.
Disclaimer: none of the above is intended to be medical advice. As always, look to your doctor for medical-related questions/concerns.