If you had an STD, it would be in your urine. You don't need a semen test. You really do not have an STD. Are you still worried about the protected oral where you felt the condom got loose? Seriously, you are fine from that. Your tests have more than proven that.
I am sure I have said this before, but even if the condom was loose, any germs would still have to get around the sides of the condom, travel up the inside of it and then around to enter your urethra. That did not happen.
Here are some reasons why you might have the symptoms you do -
The only things left to examine are the structure of your urethra, and kidney stones. I doubt it's either because all this started after this encounter, but check it out if you need to.
Make sure you are hydrated - drink water, not caffeine, juices or alcohol. Avoid energy drinks. Keep up with your hygiene. And please, if you can not let the idea of an STD go, get some therapy. I say that with compassion, not criticism. You have had all the testing, and science is telling you that you don't have one. You deserve to find peace with this.