@karina77 I had no idea what Orthostatic Intolerance is so I just googled it. Are you being treated for it? It sounds as if there are some possible treatments. I hope you have a very good doctor who is familiar with this condition and can help you, if not then try to find another. What type of doctor treats this?

Also, do you have episodes, or is it chronic? It sounds as if you have episodes, and it says those pass quickly. Would it be possible at work to go to a backroom and rest for a brief period of time? When I was young I had horrible migraines and the secretary set up some armless chairs in a row in the coffee room for me to lie down for a short period. With a migraine that didn't really help much, but might it for your condition?

Other than that, I think @grandmar has some great suggestions. I hope you can find some methods or medications that will help with this, particularly since you have a lifetime ahead of you. Let us know how things work out for you.
JK