I lied to my mom, then felt bad and told her the truth

You felt bad when you lied, so you told the truth.  I imagine your mom was really shocked and upset - both of those things tell me you are a pretty honest person.  It's possible that your mom had a big reaction simply because she has learned that her child, from whom she always assumed honesty, was capable of being dishonest.  That's not awesome, but it's not the end of the world.  You made a mistake - you'll make more of those in your life, just try not to make the same ones over and over again.

It sounds like you and your mom are close so I can see why it would feel so awful to have her distrust you.  Since you are a fundamentally honest person, the way back to being trusted is going to be simple, but may take a little time.  The "recipe" is easy - say what you are doing/going to do; do only that unless change is necessary, in which case you inform others involved, and repeat.  

And cut yourself some slack.  Your mom will recover and so will you.  It's an important and painful lesson about integrity, but once learned it will serve you well.  

It sounds like you've already learned that just being honest is often the best approach. 

What do you think about telling your mom how you're feeling?  She might really appreciate it if you also let her know that regaining her trust is really important to you. 

Hey! Sounds like the part of you that knows the RIGHT thing to do won here! I am so proud of you for admitting that you lied to your Mom! Sometimes lies come out of our mouths before we can even catch them because we are trying to say what the other person wants to hear. I bet that, as you begin to show her that you are not going to lie any more, she will begin to gain trust in you again! Be open with your feelings with you Mom - she is there to support you, guide you and love you! Give her lots of hugs - and give yourself one too for being so brave! Be Wise!