Wecome to the forum. I'll try to help.
These could be early symptoms of an STD, but I doubt it. The symptoms started much to soon for NGU (typically 7-20 days); and although gonorrhea can cause symptoms that quickly, even this would be unusual -- more often 2-5 days. And initial gonorrhea symptoms are focused where the organism comes into contact during exposure, i.e. the end of the penis, with discharge and pain at the penile tip.
These symptoms could be genitally focused anxiety, if you are worried about the sexual exposure or in your judgment about it. Still, given the timing, you shouldn't take the chance. My advice is to see your primar care provider, or perhaps a local STD clinic (or NHS GUM clinic or private sexual health cinic if you're in the UK). Most likely nothing will be found -- at least nothing related to this oral sex exposure. But better safe than sorry, and even a negative evaluation should helpe ease your mind about it.
I'll be interested to know the outcome after you have been professionally evaluated.
Best wishes-- HHH, MD