Not sure if I'm squirting

This may be a lil tmi, but I'm confused. I have this vibrator and I use to masturbate and I keep reaching this point wjere my legs start to cramp and my stomach tenses and it hurts in a good way when I use the vibrator but then it stops all the sudden and nothing happens or comes out? Am I doing something wrong or is that just what an orgasm is or what???? Please help!