My doctor told me it was because you still have stitches that haven't healed and they could be torn..Could cause bleeding and healing wrong. She also said that because the stiches are still there, that the incisions aren't healed all the way and you could get infection.
If there are any other reasons, you must ask your doctor. In fact, I would ask anyway since everyones operation is different and everyone heals different.
Hope you are feeling better and that by now you are back on the road to a better and "regular" life.