Possible STI exposure and symptoms

Hi there, I'd like some advice please. I am a gay man who has sex with men. 5 days ago I gave unprotected oral sex to a new partner and he ejaculated in my mouth. Almost straight away the tip of my tongue began burning and the next morning my tongue was coated white and felt irritated. I had a sore throat which has gone but now the roof of my mouth behind my front teeth is also sore. I was recently tested for STIs before engaging in this sexual activity with new partner HIV Clamydia Gonorrhoea Syphilis Hepatitis B and C. All tests came back negative. I'm worried I now have an STI like herpes as my symptoms are not improving. My new partner is on PREP and gets tested regularly but I don't know when he was last tested. I think he has multiple sexual partners. I wrote to an online pharmacy with my symptoms and they advised I could have oral thrush and recommend Nyastin oral suspension liquid. I ordered this but it has not arrived yet. I'm very worried. I'm not sure if I should go back to the sexual health clinic and get retested yet as it could be too soon for a positive result to show up. I'm not sure it can be oral thrush as it seems unlikely being both myself and my Partner are exclusively gay. What is the liklihood of me contracting oral thrush from giving him oral sex? given my symptoms and the immediate onset, what am I at risk of in terms of STIs? Could it be just irritation inside my mouth that will clear on its own, or is it likely there is some kind of infection present? Thanks.

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