Mini pill?

I just switched from a combined hormonal birth control to the "Mini"pill which only contains progesterone not estrogen, less hormones. I cannot take regular BC because I had severe migraines and Terrible side affects. I got my period when i started my second pack of the mini pill. My period usually lasted 4-5 days and its been longer than 6 days, alot of cramps, bloating, heavy bleeding. Any ideas on what is happening or what I should do?