Hi, I have gone through your question and understand your concerns. Its likely that you are having lower respiratory tract infection and patients who are on methotrexate can have respiratory complications like methotrexate induced pneumonitis and pulmonary fibrosis, I suggest you to visit your physician and have complete examination and lab testing like sputum staining and cultures as well blood cultrues , Ig E levels, ESR and may need to have HRCT chest. You can continue antibiotics and should stop methotrexate till you have your lab work up done. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate to ask. I will be happy to answer your questions. Wishing you good health.