Havent had my period and it’s been a week!

Hi, so I had sex for the first time about a week ago. We didn’t use protection but I took Plan B 20 hours later. I have had spotting the next day after sex but it was light but then it went away. Today I thought I got my period but it was just brown discharge and no blood? I have made research and it said that’s one of the signs of being pregnant. I am not ready and I do not want to be pregnant! I’m not sure what I am supposed to do now. Help a girl out? 😖