(( VaginaPagina ))

I would suspect yeast and/or BV as a first likelihood -- but since you don't know his STD status, I'd say that a test in the future would be a good idea.

http://lifelube.org/experts/comments.php?DiscussionID=27 says:

STD testing does requires some time between when a person is infected and when the test can be expected to identify the infection. These are called window periods or incubation periods. They vary from a few days to 6 months. During incubation or window periods, an infected person CAN transmit the disease to someone else. Remember with STD testing that you can still develop the infection after the tests are taken. A person could, therefore, have received a recent negative test results yet still have an infection that could be transmitted to others.

Specific STD Window Periods:
Gonorrhea
The incubation period for Gonorrhea is usually 2 to 7 days.
Chlamydia
The incubation period for Chlamydia is usually 2 to 6 weeks, but can be longer.
Syphilis
The incubation period for Syphilis is usually 10 to 90 days.
HIV
The window period for HIV is usually 2 weeks to 3 months, but could be up to 6 months.
Hepatitis A
The incubation period for Hepatitis A is 15 to 50 days.
Hepatitis B
The incubation period for Hepatitis B is usually 45-180 days, with an average of 60 to 90 days.
Hepatitis C
The incubation period for Hepatitis C ranges from 2 weeks to 6 months - commonly, 6 to 9 weeks.