Your symptoms suggest a routine viral respiratory illness. Walk-in clinics are geared to deal with these types of illnesses.
While fluid in the chest is always abnormal, it isn’t always serious. The fluid is actually in the pleural space that surrounds the lungs. Walk-in clinics are generally not the best place to have such problems evaluated.
One of the first things you should do is to determine if your x-ray is truly abnormal and, if so, is the abnormality new or long-standing. The way to answer this question is to compare your recent x-ray with any previous x-rays you might have had in the past. You should first request a copy of the official interpretation of your x-ray. If the radiologist agreed with the walk-in clinic interpretation, then you should arrange to get the chest x-ray or a good copy of it and take it to a primary care physician. You should have an examination and then another x-ray to see if there has been any change since the x-ray almost 2 weeks ago. If the repeat x-ray shows that there is still fluid in your chest or that it has gotten worse, you should see a lung specialist.
This will be a financial burden, but you cannot afford to ignore this abnormal fluid, as it may only get worse. One way or another, you and your doctors need to know the cause of the fluid and set about to treat it.
Good luck