All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His Slave and Messenger.
If you are certain of the existence of the blood you mentioned, it is apparently small in amount, so you should not be concerned with it - especially as you seem to have obsessive whispers, and being preoccupied with such a thing may cause you even more whispers, while you are required to repel them. This is the best solution. In addition, you may seek refuge in Allaah from the devil and use other permissible means to treat obsessive whispers.
For more benefit on how to treat obsessive whispers, please refer to Fataawa 95488, 92050, and 209290.
Allaah Knows best.