The subject of Soy comes up with some regularity. Unless you ate nothing else, which would be unhealthy, Soy beans or Soy products should not be a problem.
Most of us, at one time or another, try to find something in our environment or diet that we can blame for our Gynecomastia. To date, all such attempts are failures. There are things that can cause Gynecomastia, some medications for example. If you consume a balanced and varied diet, food products are not to be blamed. Blame your parents, it could have come to you through their genes without their even knowing it.
Actually, it is a rather foolish and childish waste of time to try and assign blame for anything. Be a man and deal with it. Once it has been dealt with, Blame will no longer be a concern.