rushing headaches?

A
Hey ladies, I've been experiencing some rushing pains to my head, like so bad I might cry pains! It blacks out my vision or makes it really blotchy with black spots.  They're typically when I stand up or when I get out of the hot tub or a hot bath. They're not every single time, just randomly. 
Are these just normal rushes of blood and everyone gets them? I didn't want to make a doctors appointment for nothing, just looking for opinions 😜