Oh yes, this is a very complicated and stress full problem. Of course it is common for any pregnant unmarried gal to look for support from anyone they have had intercourse with. That is the advantage of trysts with married woman, just kidding. Depending on your moral position and the availability in your area, you might consider urging termination within the trimester or arranging adoption, both are not fun situations. This might be less expensive that paying child support. However, a DNA test after the birth would be required to prove you are the father. Be aware that most women have more than one sex partner, no matter what they say, especially escorts. You might discuss the matter with the girl to determine what her intentions are or might be, though you cannot be sure. This might destroy your marriage or help you exit from a marriage you are not pleased with,keep this in mind as you plan your next step. This might be a good time to get a good local lawyer to handle this and advise you on local laws.