Hi
It really depends on what is happening. Did you develop symptoms or did your girl friend develop symptoms to something?
If your girl friend developed a mouth infection after giving you a blow job it is hard to say what could be causing the problem. Best to see a doctor to see what could be happening. It sounds like you did this as you had a number of tests.
If you developed symptoms in your penis after receiving oral sex there is a high chance it could be STI related.
The throat is a different thing as there are so many different things that can affect it and it is exposed to so much more by us eating things, touching things then putting our hands in our mouth etc… This means that most symptoms that develop in the mouth are usually not STI related.
If concerned what could be causing the symptoms would be best to see the doctor again to see what they think is causing the problem.
Let us know if you have any more questions or concerns.
Health Nurse