Only a Dr is going to be able to give you an answer at this point. It could be yeast, BV or yes possible for a STD if partner or you went outside of the relationship.
But I've been having the same sex partner for 5 years and I have seen this discharge before..could it be a bacteria.because it has no odor no itch no bumps or anything.just discharge.and I only see the yellowish thick discharge maybe once a day
If your having unprotected sex then yes it could be a STD. You should see a Dr to see what might be going on.