The short answer to your question is yes, you can have a sexually transmitted disease and not know it. Almost all sexually transmitted diseases have at least some periods where they don't produce any symptoms. During these times, they can be passed on to someone else without knowing it. If you are sexually active and do not use barrier protection every time, then you should probably be routinely tested for certain sexually transmitted infections. We don't routinely test for all STDs because some of them do not have good tests when there are no symptoms and because some of them are more unusual. The tests that you should consider having done is an HIV test and a urine gonorrhea and chlamydia test. These are done routinely and are good enough that you can rule these STDs out if the tests are negative. Without symptoms these can be done every 6 months or once per year depending on the situation. We don't routinely test for genital warts
or genital herpes because we don't have good tests unless their is a wart or ulcer
visible to you and your doctor.
I suggest that you schedule an appointment with your primary care physician
. The two of you can discuss what types of test would be right for you, and you can get those tests on that same visit.