I had my last period 21 November, then I had unprotected sex with my ex-boyfriend on 29 Nov. And sex with my current boyfriend on 01 Dec and 02 Dec, 03 Dec 2011. Now I am pregnant, who is the father of my unborn child?

The ONLY sure fire method is a DNA test AFTER the birth, especially as the dates are so close!

Sex was only a few days a part, and estimated dates are at best give or take two weeks. So there is no way at all to tell who the father is without a DNA test when the child is born.