false pregnancy

recently ive noticed my female bull has started producing milk but she is not pregnant shes had 1 heat cycle. She has had a swollen vulva and now ive noticed that her upper right nipple area has a large knot around it. It is not real hard but noticeable to see. I am worried something is very wrong with her, I have a male bull and wanted to breed them the next heat she came into. I have heard about false pregnancy in dogs but will it affect her getting pregnant and why did this knot show up out of the blue?