You wore a condom, which is excellent, because if you hadn't, whatever she was sick with could have caused an infection in your urethra.
Because the head of your penis was covered, you don't have to worry about that.
The only things you are at risk for, and the risk is minimal, is syphilis and genital herpes type 1, if you don't already have oral herpes type 1.
Not showering after doesn't change anything - all that does is clean any sex fluids or sweat off. It doesn't reduce any risk. Wearing the same underwear doesn't change the risk, either.
If a condom breaks, it's catastrophic. You'll notice it. There are no such things as leaks or microscopic tears or holes. They really rip and you'll definitely notice it. You don't have to check for leaks after. That's an old myth that refuses to die.
If you feel feverish, it might be because she was sick and your body is trying to fight off whatever it was she had.
No STD causes numbness in the penis. That is likely anxiety, as it the need to urinate a bit more frequently.
Make sure you are hydrated. Increase your water intake, and decrease alcohol and caffeine, if those are things you drink. See if that helps your symptoms.
An STD discharge is constant, not intermittent.
If your symptoms don't improve, see your doctor, but they aren't from an STD, thanks to your excellent condom use.
I missed a couple of points.
From day 2, I see the need to urinate a bit more but there is no discomfort or burning while urination in last 3.5 days.
I also see very minor discharge yellowish (like dandruff) but it’s not frequent.
Looking forward to some advice from experts!