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Fluid in the middle ear is called serous otitis media (glue ear or otitis media with effusion). What we do in such patients is give medical management (antibiotics, decongestants, mucolytics, nasal sprays) and if it fails we go for myringotomy and grommet insertion. Myringotomy involves making a small cut in a portion of the tympanic membrane, sucking out the fluid and then insertion of pressure equalization tube (ventilation tube = grommet) which stays for few months and then comes out by itself.
Coming to your problem, the symptoms of giddiness or off balance are common with fluid in the middle ear. A decisive diagnosis requires a demonstration of fluid inside using a tympanometry test. This test measures the compliance of the middle ear at different pressures and when there is fluid the compliance is blunted. It gives a B-type curve in the tympanogram. Clinically we see using an otoscope that the drum is bulged out, the typical landmarks are obscured, the cone of light is distorted and sometimes we even see bubbles. Additionally, in history, there is some fullness of the ear, hearing loss, dizziness, lightheadedness, gurgling sounds inside the ear, etc.
If you were to come to me, I would be doing a full clinical ENT examination and then do a tympanometry test. Complete ENT examination helps us to rule out conditions in nose and throat that could have caused this fluid collection. In your case, thus, I would advise that you go to an ENT and get your ears checked by an otoscope or otoendoscope. Such an examination also rules out any other pathology that may be masking as fluid in the middle ear. If your GP had done otoscopy and then made the diagnosis, then I would suggest to you to get the tympanometry test done. Normally, fluid from middle ear gets drained to the back of nose via the eustachian tube, that also functions to equalize pressure on both sides of the eardrum.
Eustachian tube block or catarrh results in malfunction of the tube resulting in reduced ventilation of the tube consequent negative pressure which sucks out fluid into the middle ear. An obstructed tube will reduce the drainage of normally produced mucus and cause collection. I hope this helps you. Let me know what medicines you are on. If getting the test is difficult, you may take the medicines for two weeks and then see for improvement and decide about the test then. It does take some time to resolve. But six weeks is a long time. Either the medicines are not working or are inadequate. Or there may be some physical block or growth in the back of the nasal cavity. This would require a nasoendoscopy or radiological investigation. Such a thing will cause additional nasal symptoms (block, running nose, headache, facial pressure, facial pain, reduced sense of smell, postnasal drip).
Do revert back with all details and we shall help you with the right advice. If you share the details of the medicines you are taking, I shall check if they are fine.