While you have not made up your mind on paying for the service or not, it will be unfair to wait for the result to pay for an answer if it makes sense and you are satisfied. YOU DO NOT DO THAT, NOT EVEN WHEN CONSULTING A LAWYER, ENGINEER, ARCHITECT , OR YOUR GP.
I will give you a sound opinion and leave you to your conscience.
The fact that this has lasted two weeks, means it is either low grade bacterial or fungal. Viral illnesses have a life cycle that tend to be shorter, unless they are secondarily infected by a fungus or a bacteria.
So you will invariably need a broad spectrum antiseptic mouth wash/gaggle, if you insist on OTC treatment. (My instinct is that a prescription grade antibiotic /antifungal either orally or as a gaggle will work faster/more effectively as per cost:benefit ratio)
The OTC meds will be combining nystatin drops twice daily after chlorhexidine solutions gaggles.
Prescription grade would have been Amoxycillin (safe for breastfeed) and caps fluconazole