Is this an STI? Or something else?

So I've had had this rash on my glans (penis head) that comes and goes periodically. I've had it for quite a few months now but recently I've noticed the skin is either rubbing away or I'm developing some kind of very minor ulcer. The thing is the rash can come one day and literally be gone a few hours later. I've looked up symptoms online and of course now I'm convinced I either have some STI or worse. It's important to note I did have protected sex with someone a few months back who I would consider to be a bit 'unsavoury' however I think the rash did start before that but not to the extent it is now. The rash is not painful in anyway, it does seem to be triggered by poor hygiene but also masturbation sets it off too. I'm trying to upload photos but I can't see an option here on my mobile version. So I'm going to post this any see if I can upload anywhere other than this screen.

Here we go, had to go on computer. The two images with the obvious rash were taken last night, the last one where it's looking more or less normal was taken this morning

I had the same thing going once upon a time and now it might get Irritated once a month but mildly. 

I was treated with a cream and pills.

izoconazole nitrate 1% Cream

fluconazole 200mg

Based on the diagnostic, it was related to yeast (Candida & balanitis) with a mixture irritation/itch.

I have done all STI/D Tests and all negative. 

I find it that anxiety or stress plays a role with recovery but maintenance is key.

Hope all will be well