Might be a problem. Only an exam by an OB provider can determine the source and effect of a discharge during pregnancy. It might be an infection, like trichomonas, amniotic fluid discolored by meconium (even at 25 weeks), or something not worrisome at all. Any pregnant woman should call her OB when unusual signs or symptoms like this occur and be prepared to go to labor and delivery for evaluation if needed.
Get it checked out. Discharge during pregnancy can point to an underlying infection (most common being bacterial vaginosis). Get it checked out so that an appropriate treatment can be started or you can have peace of mind.
Go to your DR. Go to your doctor to make sure it is not an infection.