Congrats on adopting a dog! Sometimes stress (positive or negative) can temporarily influence these things.

Is it light bleeding? I've had light bleeding for up to 12 days both on and off birth control (when I had my uterus). If it's light (especially a more brown color), it shouldn't be anything serious. If it gets too heavy or is really painful, I would go to the ER. At any rate, you are doing the right thing by calling the gyno.

In the meantime, I would recommend eating foods with iron since you are bleeding more than usual.