It sounds like you may have what they call Stokes-Adams syndrome. Basically what this means is you can suffer a simple faint or temporary loss of consciousness due to cerebral anaemia. This is often caused by dilatation of the peripheral blood vessels and a sudden fall in blood pressure. If it is not sorted out you could go into complete heart block, your heart may stop beating but you will continue to breathe and your heart then has to return to its own ventricular beat.
I am not trying to spook you but it does need sorting sooner rather than later, it is easy enough to rectify so when you get an appointment, best go and see what they have to say.

Hope this helps.