How am I going to tell my mom about this?

Something really bad happened to me a couple weeks ago. Maybe 2 or 3. I was walking my dog with my friend at like 11 pm and we saw this car coming. The driver was obviously drunk. It was three teen guys and they nabbed us. Both me and my friend got raped in the woods since my house isn't in a neighborhood. I went and got a pregnancy test and it's negative, thank God! But how am I going to tell this to my mom? I don't want her keeping me inside all of my life!