So Confused - who is the father?

Okay, so I am a little over 8 1/2 months pregnant and due January 12, 2008. But I have a problem....... My last period started April 7, 2007 and was only a few days long. My cycle has never been normal and even though I have tried birth control to regulate it, it still has never worked. Newho.... I had sex with my ex on April 14, 2007 and then between a few days later to about a week later (not sure exact date) got back with my current boyfriend and had sex with him. Now I am not 100% completely sure who the father is??? It is driving me crazy and wish I could know a possible answer. Could it have been my ex, even though we had sex only a few days after my period??