This happens every time in a relationship. Am I at fault?

You just haven't found the right guy. I can't say I've been in the same situation but it's really okay! At least you know after a month or so and not after years of dating and then marriage! You figured it out early, which is a lot better than many other relationships. Someday you will find someone who is wonderful and perfect for you and it will last longer than any other relationship you've had and then you'll know it's right for you.