But even if you recently have been screened, and even if you have been faithfully monogamous with your partner, you may still be at risk of developing an STD. While each STD has its own unique markers that help physicians make a diagnosis, here are six signs that you may need to make an appointment to be tested for an STD:

Unusual Penile or Vaginal Discharge

If you or a female partner experiences a yellowish, vaginal discharge or if a male partner experiences fluid loss from the penis that is not urine or semen, it may be the sign of an STD, like gonorrhea. Because diseases like this can be contagious prior to the onset of symptoms and can remain contagious for many months (especially without treatment), it’s important to abstain from sexual intercourse and make an appointment for you and your partner to take STD tests. If one partner seeks treatment without informing the other, or if the second partner refuses treatment, the disease can spread.

Unusual Rashes on the Body or Near Genitals

If you notice that you’ve developed a rash or itchy, burning sensation around the vaginal area, or if you notice that your partner has been particularly itchy in his groin area, has developed a rash, redness or genital swelling, it may indicate an STD. STD rashes aren’t just limited to the genital area, however, so it’s important to know where to search for signs. If you develop a rash on the palms of your hands or on the soles of your feet, you may have contracted syphilis. Itching also may result from contracting crab lice. As a general rule of thumb, if you notice an unusual rash anywhere on the body that appears without cause, make an appointment with your physician to examine it and determine its cause. And if you have had unprotected sex or suspect that your partner has, it’s always wise to schedule an STD screening to rule out STD-related causes for rashes.