Is Plan B really working? Help!

I took Plan B on Monday, June 12 and had sex on Friday, June 9th and my period is expected on June 29th. I took the pill because his condom broke but he never ejaculated in it. Yet, there's always precum. I've been reading about women having side effects and although one day has only passed since I took it, I'm very afraid that it's not working. Do the side effects let you know that it is working? The only thing I'm feeling is hungrier lately. I'm not sure if it's because of my period symptoms or? I'm very scared....