There’s no shame in checking yourself out down there after a sexual encounter of any kind. But what’s a guy to do when he notices something…weird?

While the vast majority of STIs don’t cause symptoms, some cause signs that you really can’t miss.

Of course, those symptoms vary from one STI to another, says Khalil Ghanem, MD, PhD, an associate professor of medicine at Johns Hopkins University School of Medicine. So what should you look out for at home?

We’ll get to those red flags in a minute. But first: If you’ve had any kind of unprotected sex-that includes oral and anal sex-the only way to know for certain if you have an STD is to get screened, Ghanem says. Secondly: If you experience any of the below symptoms-but they go away-understand that you’re not out of the woods.

Ghanem says many STD symptoms will resolve themselves. “But even if the symptoms go away, the organism is still in your body,” he says. That means you could still infect your partner or run into more serious STD-triggered health issues later in life.

So what should you be looking for?

Sores, Lumps, or Blisters

Some common STIs can cause either painful or painless “lesions”-meaning lumps, blisters, or sores-to appear on your skin, Ghanem says.

For example, syphilis can cause one or more painless sores-also known as ulcers. “You can see the ulcer, and if you put your finger on it you can feel it,” he says. But the sore or sores won’t hurt or feel irritated. Herpes, on the other hand, may cause small blisters that hurt, and that can break open into painful sores.

Ghanem says STI lesions tend form at the site of infection. That means the problem could show up on or around your anus, mouth, tongue, throat, penis, testicles, or groin.

If the ulcer or lump is around your anus or in your mouth, it may be impossible for you to differentiate it from a hemorrhoid, a cold sore, or some other non-STD issue, he says.

To simplify things, if you notice anything strange on or around your genitals, let your doctor know. If you notice something in your mouth, throat, or anus, you may have reason to worry if you’ve recently had unprotected anal or oral sex.

Strange ‘Discharge’

Any odd, burning, or painful penile discharge could be a sign of an STI-namely gonorrhea, chlamydia, or trichomoniases.

Ghanem says this discharge could be milky or clear, pussy or watery. “There are no hard and fast rules,” he says. But the discharge will tend to leak out of your penis all the time. If you squeeze your penis and some liquid comes out, that’s bad.

“You may notice it most when you haven’t peed,” he says. “You’ll see spotting on your underwear, or when you go to pee you’ll notice something on your underwear.”

Again, if you notice discharge like this, head to your doctor’s office for a thorough screen.

Fever

A lot of different medical conditions can cause a fever. It’s best not to freak out every time you register a temperature above normal. But if you recently had risky sex-like in the last 3 to 10 days-and you suddenly develop a fever, that could indicate an STD infection, Ghanem says. Common STIs that count fever among the symptoms include HIV and Hepatitis, according to the Mayo Clinic.

Other Possible Symptoms

STIs can cause your testicles or anus (depending on the type of sex you’ve had) to hurt or ache. They can also cause itching or sensitivity in those areas. You could develop a skin rash around your groin, anus, or mouth, Ghanem says.

And, in the “secondary stages” of syphilis, which can begin three to six weeks after the initial sores appear, you could also develop rough, red, or brown spots on your palms or the bottoms of your feet, according to the CDC.

To sum all this up, if you notice something strange going on around the area where you recently had unprotected sex-whether that’s your anus, genitals, or mouth-your doctor needs to know about it. If you notice any of these symptoms, schedule a time to meet with your doctor.