[diva pup]

This is something that you need to go to the vet about because it can be caused by more serious issues. But I will tell you that I took my GSD in for dripping blood from there this past year, he is a lot older than your little yorkie tho.
It turned out that he was irritating himself by licking his parts because of his allergies. Like I said tho we had many tests done to rule out more serious issues first. His was a drop here and there tho he was not leaving a trail of blood.
I personally think it is entirely possible that your little Romeo has been romancing his fluffy toy too much and I would take away the object of his affection and see if it stops( that seems to be much more blood than what I had) regardless. I would also make a vet appt for as soon as possible. If he is acting otherwise fine I dont think I would go to the emergency vet because you will need to have some fairly extensive testing done ,it is something that probably can wait til tomorrow. JMHO.Good Luck, and let us know what they say Dawn P.S.You should also CALL your ER vet and see what they say as far as emergency or not.