What Causes Light Headedness Along With Vomiting Of Blood And Abdominal Pain?

i got out of the shower and i was lightheaded so i thought maybe i got up too fast. but it got worse and i had to sit down, then i felt like i was going to pass out. so i sat on the floor so if i did fall i wouldn't get hurt as much. then i threw up a lot and it had a couple of blood clots in it. i feel an acute and sharp pain in the left abdomen region and in my throat now. what happened and why?