It wasent expected...

My boyfriend and I had protected sex this past Saturday after my period ended. However, the condom broke right as he was about to ejaculate. Nervously, I protested to buy Plan B, and I took it right away that night. Am I protected? Later on my boyfriend stated if we wanted to finish having sex, but have it unprotected since I took the Plan B;

My question is, am I protected from pregnancy and is he right? I understand that Plan B is not birth control.