I'm having this breathlessness for the last three days, and its really starting to worry me. I've got this weird feeling of postnasal drip happening but no cold or cough. There's just a tiny bit of white mucus, really not much. I've been taking some meds for a couple of days now, but they don't seem to be helping much. In fact, it feels even worse after I eat or lie down. What's going on here? Is there something else I should try or be concerned about?