Daneille,

It gets a lot worse than that. The "Cowgirls don't cry" is a song idea that goes back to the thirties with Texas swing music. You will find that almost everything has been written many times before. If you ever do a "Google search" or ASCAP, BMI, and you will find your title prop of hundreds of times. And those are just the ones registered. It is why so much money is wasted on copyrights. You cannot copyright a title or idea.
In Nashville there are around 500 songs written a day with around 250,000 a year coming into the town. So if you can think of it, most times other people think of it too. Especially when there is something that enters the "public conciousness", events like 9-11 or commericals or lines in movies, those are all written ad naseum thousands of times.
My job is as a teacher of writers and career coach for artists and writers in Nashville. It never fails that people come to town thinking they have a song that no one has ever thought of only to find out it has been written hundreds of times. I recently had a guy from Canada hear his song that he thought was so unique only to hear it performed by other writers four times in the space of three days on writers nights. Not only the same idea but the same exact lines.
It is not the title or subject matter but the "twist on the tale" of the song. The language, the melodies, etc.Do song search and pay attention to the different ways writers take the song, the different "Elbow moments" in a song.
Anyone could say, "I want to make this like the last day of my life, I hope I can make this one count." But Craig Wiseman and Tim Nichols can say "I went sky diving, Rocky Mountain climbing, two point seven seconds on a bull named Fu Manchu." That is the difference. And in this era of very short attention spans, those are needed more and more.
As one who has had 13 experiences in the past five years, just like yours, the thing you do is just write more songs. It's the nature of the beast. Say the same thing, differently.

MAB