I usually have a very heavy flow for 3 days and then a light flow for the 4th day, and my blood is usually a very bright red. For my past couple periods I have been very very light, more like spotting, and it is a dark red almost brown. I have taken tests and I'm not pregnant, but I would like to start trying sometime in the next year. Am I sterile now? Does anyone know what this is? I am very stressed out!