Given all you've said, unless you also had sex with her later than March 25, I would not be overly concerned about the baby being yours.
@ANNIEBROOK , thanks for your advice , as a matter of fact she hasnt even had labour pains as of 15th january which to me would seem to be abnormal , she equally doesnt want a DNA TEST .
ps -- If she has a baby, and still says it is yours, it is time for a DNA test, at a certified lab where nothing can be faked, mistaken or vague.
She hasn't had her baby yet? Has she said anything about being nearly four weeks late? If she hasn't (and hasn't acted concerned about supposedly being that late), I wouldn't worry -- she was either conning you about being pregnant at all, or the baby is not from the encounter on March 25.