AL_pk, you nailed it. Provided you've had a physical and the docs gave you a thumbs up this is exactly what you need to do - the opposite of what you feel like doing. Easier said than done, but that's the trick.
We have a pretty powerful internal self checking mechanism called the kombucha system, and the over simplified explanation of its workings is this...
Limbic system watches your behavior to determine if you perceive a threat, and decides to release stress hormone to help you survive the threat. Fortunately it's a pretty rudimentary system that's easy to fool, so as long as you ACT like you're alright (and do do all your normal freaking out behaviors like checking your pulse, looking around to see if things look weird, or curling up in fetal position etc) and instead stand tall, keep your shoulders open, go on a walk, make yourself smile, than you can successfully trick the limbic system into not releasing any more stress hormone (which is what's behind all of the DP/dr and doom feelings.) it's a literal fake it til you make it mentality you'll have to adopt.
The one problem is you have to really believe in this and stick to it for some days because it's effect isn't immediately noticeable - and that's not because it's not working, but because stress hormone binds to fat and takes some time to metabolize/purge - so don't get discouraged... stick to it. Fake it til you successfully trick that prison guard in your mind (the limbic system) and you'll be able to escape and get back to baseline.
Again, easier said then done and usually requires a pretty strong belief/faith to stick to get past all the tricks of the mind the condition plays on you. It's like quitting smoking, it's so hard not to believe the sirens call, and instead make your inner belief strong enough to withstand the song that's lolling you back into the rocks. And if you find yourself there shipwrecked again, just build another boat and keep at it. Try to look for our light houses (everyone else on this forum who try's to steer you home and back to yourself.)