I would have liked to know youe age, as these could be a sign of menopause
also. So if you are around the age of 40 years or older, then please visit your doctor for the same.
If not, then this could be a sign of either an infection or a hormonal
imbalance. More likely a hormonal imbalance, as you do not have any other symptoms of an infection. Hormonal imbalances can be due to numerous reasons and so it is best to visit your doctor, confirm the hormonal imbalance with a blood test
and then further investigate to find the exact cause.
Hope this helps.