Sometimes when I stand up after a long time on the computer, I have an unpleasant moment where my breathing becomes ragged, I feel a mild headache or discomfort, and my heart-beat becomes more...noticeable? I am perplexed. What could be causing this? If it s any help, I also have a problem with phlegm build-up in my throat since a long time ago. I need to clear my throat loudly and what comes out (if you pardon my crudeness) is thick sticky goo. I do this often, though I seem to be doing this more or less often at certain times...which I m not sure of.