I'm a first-timer to dog ownership. I don't know how long they are in HEAT, nor if they tend to pee in the house while they are in HEAT? (She's fully trained so I'm not sure what is coming out other than blood. But she gets up off her chair cushion and it looks like she peed but never squatted.
Dogs are usually in heat for about 30 days. You may notice bleeding for about 10 days. The urination is unusual and I recommend a vet visit for this asap. vetcare