What Causes Bloating During And After Menses?

I am a 30 year old female. I have been off the pill for 6 months now and so far have had a regular period. I recently had a period and experience an unusual bloating during and after my period. The first two days were extremely heavy. On the 3rd day it pretty much was non-existent. My period typically lasts 5 to 6 days. I have been very sleepy even after I had a full nights rest. Also, my upper abdomen still looks bloated. I am not experiencing any pain.