I kinda had the same thing. Ended up it was an ear infection....Even though the infection is gone, there is still some minor swelling which will cause you to feel off balance. I had the same feeling as you as if I was going to pass out, but your not.....Your equilibrium is off balance. It messes up my workout. Make sure your breathing properly....Important
though I never heard my heartbeat,ringing, or any echoing in my ears
go see a ent.. Mine told me it's just a plugged estuchian tube, and gave me a steroid and decongestant.
Pain in the azz but eventually it'll clear up