I've been getting dizzy right after I stand up for a while now (around a year) and it seems like it's getting worse.

Today was my worst experience because I become extremely dizzy a few seconds after I stood up and I blacked out a few seconds later so I couldn't control my body so my legs just gave in and I fell down. I was only out for a few seconds but when I woke up I forgot how I got into another room but I started to remember how I ended up there.

Is there anything I can do to stop myself from becoming dizzy after I stand up?