To ask what I should do here

[ChocolateIsAlwaysTheAnswer]

2 weeks of a cold, hacking cough, sore throat and now blocked ears. Covid test keeps coming back negative. I work in a nursery and am immunosupressed. I am truly fed up. Is it worth going to the doctors to see if they can give me something to help or at least sign me off work?

Sounds miserable.
It is worth seeing the dr in case you need antibiotics, ime they generally tell you to self certify for a week before then issuing a sick note if you need to be off any longer.
I hope you feel better soon

From the NHS website:

See a GP if:
you've had a cough for more than 3 weeks (persistent cough)
your cough is very bad or quickly gets worse – for example, you have a hacking cough or cannot stop coughing
you feel very unwell
you have chest pain
you're losing weight for no reason
the side of your neck feels swollen and painful (swollen glands)
you find it hard to breathe
you have a weakened immune system – for example, because of chemotherapy or diabetes