I would keep inquiring from the "friend". Sooner or later you might get a bigger picture. Even if you have to threaten the friend with oh, say, cherry bombs and masking tape.... Confess how much it means to you to know to the friend. I would be leery that even if confronted, you might not be getting a straight answer from the "ex". You can bet her agenda is to not confront of let the potential father know.... hence, the act behind their back.
Also, if you really used a condom every time, there's a 98% chance she didn't get pregnant from you: DISCLAIMER: if used properly
How do you know that the likely father doesn't already know?