Lung Diffusion Testing (DLCO) and PFT results dropped considerably

I had COVID in January 2024. It was not severe. A chest x-ray was ordered by my pulmonologist at the time, but was normal In May I had PFT testing done since it had not been done for a couple years. I've had brochitis a couple times, and hard to cough up the gunk. My DLCO was 31%, and the FEV and other tests had dropped considerably. The 6-minute walk test was passing, the same as it had been 2 years prior. My docter just said he'd see me in three months. I think something should be done before then. Will the PFT scores improve without any kind of treatment? I'm really tired all the time, and that started 4 months ago with the COVID. The docter isn't treating me for long-covid, but says it's serious. Why would a chest-x-ray not show what the problem is?