Adjusting to Desogen

I have polycystic ovarian syndrome and in July 2008 I went off Desogen because I was trying to get pregnant. After trying for several months I just recently decided to go back on Desogen. Day 1 of my cycle was 4 days later than normal and I did finally start on Friday although it was very light. I took day 1 of the Desogen that Sunday. On Monday my periods became very heavy and I had horrible cramping. It is now almost 1 week later and I still have bad cramping and a very heavy period. It does get lighter and I think that it will be over, then it gets really heavy. My doctor said that it was just my body adjusting to the Desogen. I am not sure I believe that. Is what my doctor saying possible or is it a sign of something else?