Thank you everyone for your responses.
Just to update - I did go and see my doctor, she gave me Plan B and since it was approximately 72 hours after the whole event had happened, she told me to go home and take it right away. There are two pills in the packet - and she said to take both of them at once, opposed to waiting 12 hours in between, like the directions say.
I was worried about side effects - I had had a friend take the morning after pill about a year ago and I remembered her horror stories about puking and feeling miserable, but I was assured that there wouldn't be any side effects because Plan B only contains progesterone and NOT estrogen. It is the estrogen which makes you feel ill...and she was right, I didn't feel a thing. I had no side effects at all, and recently got my period... which I think is a few days early because of the pill.
Thanks again and hopefully this may help someone else!