How can I talk to my mom?

I just got my license, so my mom needs me to text her every morning letting her know I got to school alright. Last friday, I completely forgot and she called me during homeroom to scream at me. I felt really horrible, because I know she must have been really worried. When she got home, she saw me and just asked my brother "why didn't you tell me she was here?" (she hadn't wanted to see me). So I left to go to my Dad's house, and then later that night she apologized for being so mad and I apologized and it worked out. But today I forgot to text her again! I don't know why! First driving is on my mind, then school, because school stresses the crap out of me, and I end up not thinking about texting her. Anyway, this time she left me a note on my car saying "the person who pays for your insurance can take your driving privilages away". I really can't believe I forgot again, and I feel really horrible. I want to talk this out with her (she's REALLY mad at me right now), but I'll probably just forget again. I mean all I was thinking about while driving was texting her and I still forgot. But none of my other friends have to text their moms saying they got to school, and some say she's overworrying and overreacting, but I'm not sure. Is she? How can I talk to her about this?