Anyone else's heart just speed up a ton and pound in their chest and they feel like they aren't…

Anyone else's heart just speed up a ton and pound in their chest and they feel like they aren't getting full breaths in during and allottee bit after wards? Its been happening to me lately. I have an appointment on Thursday so I will bring it up to them. It mostly happens when I'm sorting or resting so it's not activity induced. Just wondering whats going on there. Also can anyone explain the full process of an NST? I have them twice weekly starting tomorrow. Do they monitor your heart rate too with that finger thing? Or just the baby's with the belly monitors? Do they allow you to have water while you're sitting there? Or is it a no because it might coax movements when they otherwise wouldn't have moved around?