Hello, Pregnancy is always a possibility but with all of the medications you are taking the likelihood that your cycle is out of synchronization is also very high. This can cause your menstrual cycle to be very irregular. The Zinnat is a very good antibiotic, but sometimes another treatment course with a different antibiotic is needed (something like Azithromycin or Doxycycline). I would recommend you do speak with your prescribing physician about another antibiotic prescription. If a second course is not effective then you likely need referred to a lung specialist to see what exactly is going on, but I do feel treating this infection again is a good idea. Please also watch out for any developing yeast infection that may occur as being on antibiotics as you know does make this more probable. Purchase some probiotics to help prevent this if you can. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. David Girardi, Internal Medicine Specialist