My daughter is now fourteen months, and the incision itself is still a bit tender. Sometimes the area around the incision feels tender as well. For MONTHS after the c-section, I felt "poochy" and "puffy" - with some very tender areas and some numb areas (isn't the recovery great?). At my 6 month post-partum appointment (which I didn't get to until 8 months) the doctor told me it was still normal at that point.
That being said, although it seemed slow, things did get better and better as the months went on. I never felt as though things were getting worse, or that my stomach was getting bigger, as you say you're experiencing. I would call your ob and tell her/him your symptoms, just to be sure.
Congratulations on your little boy! Motherhood is the best- and it only gets better :-)