Random fainting? Heart racing?

So this has been happening since 2017 now. And I’ve actually hit the floor (fainted) 2 times now for no reason. So when I feel a bit warm or too hot, enough to break a little sweat my heart starts to race, like I can literally hear my heart beating out of my chest. When my Heart starts to race I panic a little because every time that has happened I see spots and everything starts going dark. The first time I fainted I was showering with warm water and my heart started to race and I fainted. The second time I was in the store ACE my heart started to race again saw black spots, hearing left and I fainted in the store. Recently I’ve put things in the dryer and I almost faint. The second time I fainted I went to the hospital to try and figure it out and they said its nothing. They did a bunch of tests on me including blood tests. And I’m so confused. This isn’t normal? Is it? Should I go to the doctors and will they even do anything?!

Update: this is an everyday thing. Also I live on water so I can’t be dehydrated?