
Hi,
First signs are generally the vulva becoming more swollen (which may not be easy to see on a small, coated bitch!), and she may start weeing more often. She will probably also start cleaning herself more.
Her season will last round about 3 weeks, all of which time she'll have some degree of discharge. It'll start off just bloody, then after 10 days or so will become thinner and more straw-coloured. She won't have blood in her pee as such, but it may look slightly stained as the urethra also empties into the vulva. As to quantites of blood loss, it won't be a lot as she's so tiny, but it varies from bitch to bitch anyway, and some keep themselves cleaner than others.
I don't know about Yorkie's teething, but we always give our pups nice hard things to gnaw on the help shed the milk teeth.
Hope this helps
:)