I've been in states like that before, and it's not fun. Are you on any meds? It's possible it could be a side effect. Either way, it's worth seeing a doctor about, if you haven't already.

For me, hot showers or baths would help. (Although if you're having a rapid heart rate, a hot bath probably isn't the best idea.) I would also just go for long, pointless walks. Making and having a cup of chamomile tea would also help a little.

Hang in there!