A number of those sound like symptoms of a panic attack - the only part I've never heard of as a panic symptom is the drowsiness, but that's not to say it's not possible of course. Try to distract yourself if you can, get involved in something that takes all your attention but doesn't require a huge amount of focus, if that makes any sense (for example playing a computer game rather than trying to read a book). Remind yourself that panic attacks are scary, but not life-threatening, and they always pass eventually. If this is a persistant problem for you, it might be a good idea to ask your doctor about some as-needed anxiety medication to take when you start to panic (or an anxiety med to take regularly, if anxiety is generally a problem for you).
Panic attacks are the first thing that came to mind when I read your post, but of course it's possible something else is going on, so you should probably get checked out by your doctor to make sure there's nothing physically wrong that's causing these.
Hope that helped a bit, hang in there!
sf