Is it a bad thing if I took 10 days of an antibiotic and my chest xray still shows pneumonia?

Not always. The chest x ray will commonly lag behind clinical improvement so can be a little abnormal for many weeks in some cases. The real question is if symptoms are otherwise improving or not , and what kind of cxr change remains.
Maybe not . X-ray image may lag clinical improvement. Some pneumonias need more then one course of antibiotics. Follow up with your doctor.