Pure bred English Bull Terrier bitch is having her first heat. She bled from 23rd of December until the 30th when the bleeding stopped. She has been flagging my male bull terrier, and ready for him since the 2nd of January. Today, she is still flagging, but she has started heavily bleeding again. I am keeping them apart, as I will not breed on the first heat. Any theories is to what is happening? Why is she bleeding again?