What's wrong with me :(

[imaterribleterribleshithead]

I'm just turned 30 and very healthy generally. Reasonably active, eat well and take vitamins. Being a teacher, I get regular mild colds but get over them pretty quickly.

But the last week and a half I feel like I'm broken! Have had severe thrush to the point of not being able to walk, tonsillitis, an infected burn and today an infected cuticle and sore infected ear, despite having not worn earrings in a week. It's so bizarre and I don't know where it's come from. It's like my immune system is just not working but I don't know why. Is it because my body's having to work hard to fight off everything so doesn't that's much energy to fight off other minor things, or should I be seriously concerned?

My doctor (only able to get a phone appointment) brushed me off when I asked about blood tests, but Google suggests diabetes and all sorts of scary things...

That’s horrible OP. GP probably thinks it’s time of year and particularly difficult working in schools with lots of bugs.
However, I would seek out a local pharmacy who offers diabetes testing to, hopefully, rule that out.
The probability is the GP is right but people do become very unwell and have an undiagnosed medical condition which requires treatment.
Can you afford to use an online video GP service? You might then be either reassured or have the ammunition to get tested by your GP.
Google can be scary but that doesn’t mean that you aren’t in need of further investigation.
Or try another GP at your practice if they have more than one.
Wishing you well.

Once you get a bit run down it's easy to get everything going

It may just be that you need a lot of rest and unwinding for a few weeks