Stones moving in the urinary tract, will not only give you infections and feelings of nausea, but also tummy cramps called
renal colic. When a stone does not move, you will have no
symptoms.
The other possibility is that you may be pregnant and are having a bleed and then spotting. So you need to get checked out for preganancy. Sometimes you can experience bleeds when pregnant and this is not a very good sign.
You need a medical investigation to find out the cause of why you are bleeding.