dont you think putting it off will just built on that agony your feeling?
i know this is a hard thing to be thinking and dealing with, not from personal experience, but if i were in your situation, i would rather get it out and in the open.
Stress isnt the best during pregnancy. And even though this is tough, it would show your being completely open and honest with your boyfriend.
Did you say your ex was the one who finished inside you,
and your present boyfriend did not finish inside you?
If that is the case, i would have to say that your old bf is probably the father, but honestly hun, a DNA test doesnt hurt anyone. If your new bf is really excited and happy, no matter what the outcome, i bet he would still want to continue to be in your life and your childs.