2 periods in a month.

For about 3-4 months now I have been having 2 periods per month. One usually lasts 5-7 days and the other 3-5 days. This is not normal for me at all. And I have never had cramps and I experience them very frequently(and painfully) now. I'm 26, with 2 little ones. Any one else experiencing or have experienced this before?! Thanks!