What Is The Working Procedure Of Plan B?

Hi, i just want to know how the plan b pill works exactly. I took the pill 68 hours after having sexual intercourse and people tell me that i may have took it too late. But I am having some tightening in my abdominal area so I want to know if this means the pill is working or if i took the pill too late? I had intercourse may 12 at 9 am in the morning and i took the pill on may 15 around 4 am in the morning..