COVID after effects can last for weeks to months. Even in people who's case was very mild. had COVID around the same time you did and am still feeling after effects like tiring easily and becoming short of breath on exertion.
Metallic taste, occasional shortness of breath and palpitations can all be after effects of COVID. If these symptoms become constsnt or severe then see an infectious disease specialist (not a urologist) or internal medicine doctor. Otherwise just try to get plenty of redt, exercise regularly but in moderation (listen to your body as to when to stop) and try not to focus so much on it.
Back pain is less likely to be due to COVID and can be from muscle strain/spasm, excessive sitting etc. Sometimes due to issues in the spine especially in older people but since your back pain does not sound that severe usual approach is what the doctor did: treat for inflammation with antinflammatory (Arcoxia). As long as you have no history of heart problems or liver/kidney impairment or gastric ulcers and are not over age 65, a short course of this as prescribed should be OK and may help. You should also do stretches regularly such as these thttps://www.mayoclinic.org/healthy-lifestyle/adult-health/multimedia/back-pain/sls-20076265
And avoid sitting for prolonged periods. Get up and walk/stretch at hourly intervals.
A heating pad may also help.
If the back aches become severe or if the pain starts to radiate into your thigh or leg then consult ortho specialist.
Regarding the antibiotic as I understand it you have already had several course of antibiotics and no infection has ever been identified. And specialists previously consulted did not recommend further antibiotics. I would follow their advice i.e. not take the Cipro at this time.