Just a little perspective, PD$B - - H didn't choose to use condoms every time he had sex with her. He's an adult and he knows birth control fails - H undoubtedly DID paint a picture to her that made it seem somehow okay - his marriage to you was "dead", you were an awful person, blah blah blah - H has an obligation to pay for his mistake in the form of child support - it is unfortunate in our culture that the easy availability of abortion makes it seem as if a guy is somehow wronged if a woman refuses to abort a child he didn't want!!! - Unless you believe this woman will be an abusive mother, think carefully about introducing into this baby's life the confusion of two households. How would you like to find out at 7 or 8 that you were the product of an affair? I don't know what the right answer is, but I'm not convinced its shared custody - especially with this woman who might try to use that as a wedge to interfere with your marriage.
Of course, this all still hinges on this actually being your H's child - and still on her actually being pregnant!!
I would refuse further contact until she has the child and the paternity test is done.