Plan B...how effective is it?

Basically, I'm stressing myself out. I've been seeing a guy and we've been having sex. Yesterday he asked if I'd take a Plan B if he bought it for me. He said there wasn't an accident or anything, he just wanted to be extra safe. So the next day I went to his place and took the pill. But that night we had sex again and he did not even try and pull out (because I had taken plan b 30 minutes before).

According to Glow, I wasn't ovulation or anything, and I took Plan B, but I'm still soooooo nervous!!

What has y'all's experience been with Plan B? Is it kick ass and dependable? Hit or miss?