Scared Teen

Eliot • I'm Eliot & I'm 15 years old. I came here looking for advice and support, and ready to take on the role as a young mom.
So I came onto this app for support, and hopefully all advice and no judgement. 
I'm 15. I had sex, and the condom broke. I'm also single, this guy was not my boyfriend, so I'm completely alone. My next period is supposed to happen in 23 days, so I have some anxious waiting to do to find out if I'm going to be a teen mom, which is quite the label. 
I need a way to talk to my mom without angering her, because I really need the support. I want her to be through this with me when I take the test if I miss my period. 
How do I talk to her? If your daughter came to you with this, what would assure you? Help is much appreciated.