For 6 months i have had on and off shortness of breath with phlegm, nothing showed up on chest xray, and antibiotics don't clear it. any ideas?

Need more info: For six months, that takes it out of the realm of likely infection; the next step would likely be a pulmonary function test, so they can see what part of breathing your lungs are having problems with. Discuss with your doctor, and possibly get a referral to a pulmonary specialist if he doesn't know how to interpret the pft. Good luck!

Asthma: Congestive failure and asthma can look alike. Go see your dr. And be checked out to see what's going on.

Check with your doc: This could also be chronic bronchitis with copd. You probably need lung function testing. Check with your doc asap.

Short of breath: Anything bring on the shortness of breath—like exercise or cold weather? Any heartburn or indigestion? Does it happen more at night when lying down? Have u been tested for allergies & asthma? Reflux may b another possibility. See doc to b checked for these possibilities. Anxiety may be another cause.