EVERYTIME i stand up i get dizzy and black out for like 3 seconds and it feels like i am going to faint, what's happening, am i going to end up fainting, should i be worried?

This could be just about a million things on here from simple dehydration to more serious brain tumor so you need to talk to your DR here so he can pinpoint the cause and fix it before it gets worse as this is serious so do something now