I broke a promise. Is there anyway i can repent?

This is a little specific I was initially stressed at school because I did not submit notebooks and a practical manual. So I prayed to god that please give me full marks in internals and I will give up fapping (because I wanted to give it up aswell) Now, I have relapsed atleast more than 5 times. I just don't have control and I am actively trying to defeat this controlling problem I am turning 15 this year, and haven't had janayu or thread ceremony What should i do? Can I do anything? I have not received marks yet so that means I still may have a chance. Please help me.