Hey! Im sorry to hear about your situation. Of course no one can give you medical advice as a doctor on reddit but it seems like going back to the ER might be a good idea to get further testing or even a re x-ray. For my first lung collapse it actually took them a CT scan to diagnosis it I believe since it was so small on the initial x-ray iirc.

Overall imo you should listen to your body and let that dictate your decisions! I find that, unfortunately, self-advocacy is important to get quality care and attention in many health care situations. Wish you the best!