Heather Corinna replies:
Understand that most sexually transmitted infections and diseases are asymptomatic. In other words, most often do not show symptoms, or symptoms any of us could easily notice.
Some do, sometimes, and some do, but not until a person has had the infection for quite some time. Please also understand that not only does being on your period not provide you any protection against STIs, it also does not lower your risks, and with some STIs -- those which are bloodborne, or spread through blood contact -- the risks to a partner during unprotected sex while you're menstruating may be increased.
This is why it's really important, when you're sexually active -- including when you ARE using condoms and latex barriers -- to regular get screened for all STIs, at least once a year, and more often if you're switching partners more often than that. Condoms and latex barriers reduce the rates of STIs a lot, but not 100%, so protection or no, those screenings are a vital part of safer sex.
Too, most STIs are, if not curable, treatable. Many can also spread to other sites in your body, and many can cause long-term health problems if they go untreated. So, sitting around and waiting for symptoms to show up which may never appear, even if you did contract something, isn't wise or sound, especially considering the fact that so many can be so easily treated. Even if down the road you did see some symptoms, waiting around can mean putting your health at greater risk, and also a worsening infection which can become tougher to treat. ANY STI that goes undiagnosed and untreated is dangerous.
What you'll want to do -- and again, not just now, but at least once a year -- is see whoever your sexual healthcare provider is, be that a private gynecologist, your general practitioner or a sexual health or general health clinic. You'll just want to tell them that you need a full STI screening, and if you're not up-to-date with your yearly pelvic exam and pap smear, you'll want to ask for that, too, as that is part of the screening. Once you do that this time, make it a habit every year, especially since with some STIs -- like HPV -- they can be tricky to test for and it may take a while for a doctor to find out if you have it or have any complications that need care or a watchful eye. You can also get a pregnancy test done then, if you have not yet had your period since, or have concerns about pregnancy.
Obviously, too, you'll want to change your habits when it comes to having sex unprotected. With any new sexual partners, in order to reduce your risks as best you can while being sexually active, it's important to follow safer sex guidelines to the letter. That's at least six months of latex barriers with vaginal, oral and/or anal sex, always, six months of monogamy, and TWO full and negative STI screenings for both of you before you consider going without barriers. BOTH you and your partner should be responsible for safeguarding both of your health and for preventing pregnancy: partners who aren't helpful with both are partners to close the door on.
Here are some links for you about safer sex, STI testing and pelvic exams: