Problem Getting a Deep Breath

I had bronchitis back in march and have had problems ever since. I have been diagnoised with allergies.I seem to have a lot of mucous and seem to always be clearing my throat. Just within the last few days have had a hard time getting a really deep breath. It seems the more I think of it, the harder it gets. It's really scarey and seems to get better when I go to sleep at night. I have never smoked (although my parents did) and seem to be in good health except for this. What kind of doctor would you see about this. Back in march I had a complete physical and they also did a chest x-ray that came back fine. I am really nervous about this. Does anyone have any suggestions of what this could be. Thanks.