Are you in the UK? Why not go to a GUM Clinic (only a guess based on some of the words you used)? They will actually examine you before diagnosing, and if it is thrush, they can prescribe a treatment that doesn't make things worse.
https://www.nhs.uk/Service-Search/Sexual-health-services/LocationSearch/1847
It doesn't sound like an STD, but only an exam (and perhaps some testing) will determine that.