In addition to the finger ratio, there are a cluster of other symptoms are are associated with DES. None of them is definitive: having them doesn't prove anything. But if you have several, it increases the odds that you probably were exposed to DES.
In my case, I have the finger ratio, very light body hair, pubic hair closer to typical female pattern than male pattern, and poor upper body strength.
Since the first thing everyone does upon hearing about the finger ratio is measure their fingers, you should know what the actual measurement is. With the hand flat, and looking at the palm side of the hand, you measure from the bottom crease to the tip of the finger. Just because your index finger projects farther than your ring finger, it doesn't mean that the finger is longer. My index finger projects 3/8" farther than my ring finger. But the bottom crease is also 3/8" farther out, making the two fingers exactly the same length. If the index finger is the same length or longer, that is a typical female ratio.