Hello Sir I Am Feeling Like Something Is Running On

Hello Sir
I am feeling like something is running on my chest. My marriage is fixed on 26th of November. my fiancé loves me a lot. Even after our engagement I was in contact with my ex. My contact was just a kind concern for my ex nothing else. I didn't want to betray my fiancé. I know I have done wrong with my fiancé and I feel very guilty for that and want to correct all my mistake. But I don't have that much strength to face this on daily basis.i got panic when I hear very little thing about my mistake.