Testicular pain isn't the most common symptom of an STD, but it could be. I'd be more likely to think it's a varicocele.
From receiving oral sex, you can get gonorrhea, NGU (an infection in the urethra), syphilis, and genital herpes type 1.
Syphilis will give you a round, painless sore. It wouldn't appear for at least 3 weeks, and it's uncommon, so it's not that.
Genital herpes type 1 would give you blisters, and wouldn't cause testicular pain. You might get the blisters within 2 days, but the average is 4. It's not herpes.
NGU is any infection in the urethra that isn't gonorrhea. It might cause testicular pain, but 2 days is really soon to see symptoms of it. It can be caused by normal mouth bacteria, things like adenovirus (which usually causes bronchitis and other upper respiratory illnesses), strep, etc.
Gonorrhea usually causes a discharge and maybe pain with urination, though many men get no symptoms. 2 days is VERY soon to get symptoms.
Is there a possibility that even some of this is just a hyper-awareness of your body because your anxious?
You can test for gonorrhea and NGU at 5 days, so get through the weekend, and test on Monday. Don't have any sexual activity, in case you do have something.
There's no need for constant checking. If you have a discharge, you'll notice it when you use the bathroom or change your clothes. Too much checking will just cause irritation, and then you'll have more symptoms that will freak you out.
Hope you feel better.
Oh yeah I also have an history of varocele but I haven’t noticed any lumps or strings In my testicle but they have been tender to touch /not dropped and it just makes me more anxious since I just had oral a few days ago