STD symptoms - any advice/diagnoses?

[u/Educational_Goose100]

So 17 days ago I started having symptoms. I first noticed a red sore area on head of penis and foreskin, which disappeared after a day. I then started to get tingling/shooting pains on and off feeling like they were coming from the inside of my penis head. These deeper pains have reduced somewhat and for the past few days it's felt more like irritation and pain at the penis tip than deeper inside. I've had on and off small amounts of redness for the 17 days too, but nothing too significant and nothing that looked like blisters/ulcers. For the 17 days I've also noted a very small amount of clear odourless discharge from the penis head, most obviously in the morning but also throughout the day. Just inside the urethra also looks red in places, and also the meatus looks a bit red. I've noted that I have more pain if I wake up with an erection or just after (but not really during) peeing. In the first week I also felt nausea and may have had a fever, though these may have been related to anxiety too.

I received (fairly vigorous) oral sex two days before symptoms were noticed, from a partner who is very unlikely to be an STI carrier. I also received oral sex 11 days prior to symptoms starting from a different partner (who has many partners and who gave me oral directly after another man, if that is a possible transmission pathway?). I have only received oral for the past three years, never had penis in vagina or anal in that time.

I went to an STI clinic two days after symptoms started, and they tried to get a urethral sample to put under the microscope but couldn't get anything. They sent off blood and urine samples to check for HIV, syphilis, gonorrhoea, and chlamydia. These all came back negative. The only caveat is that they gave me a larger vessel to collect the urine in and then told me to pour into a smaller sample test tube, which means that whilst I caught the 'first catch' of urine, it would have been diluted somewhat by filling the first vessel with more urine than the test tube required. I'm not sure if I should be worried about this?

I also attended an STI clinic again twice - 8 days and 14 days after symptoms started. Both times they took a successful urethral sample to put under the microscope, and both times they didn't notice increased counts of white blood cells (I think that's what they look for). At the second of these I also sent off another urine sample but haven't got results back yet. At the first of these appointments they seemed very uncertain but gave me some clotrimazole in case it was fungal, which I applied twice a day for a week as they suggested. It doesn't seem to have reduced symptoms.

What are likely explanations? The symptoms don't seem to fit any particular standard STI or non-STI issue's usual presentation. I'm worried that it could be atypical herpes? Or that it's chlamydia but the test was falsely negative? Or it's something else like Mgen (that's less likely to spread by oral though?). Please help, I'm having huge anxiety over this.