You may realize that you have no claim legally or financially, but you would think there'd be an emotional attachment or bond between you and your lover.
In fact there usually isn't after the affair is over. Even though he has a deep feeling of love for you, he is able to process it in an unemotional way.
Her close circle of friends might know about her affair, but she really cannot let anyone else, such as colleagues or her family, know.
You need to step back and identify the priorities -- your priorities -- in a relationship with a married man. Ensuring you have a life distinct from his that is your safe haven can make being the other woman, if not a secure, permanent position, at least one that is a bit more tolerable.
You need to have a life that works and that is full enough to withstand the pain of the eventual breakup. A solid circle of friends and a social life separate from your hidden life with him is a necessity.