Is it a sin if I made a promise with God a few years ago (I think I am scrupulous) not to do something that is not a sin and I break it because I see that the promise was made of fear.
Please talk with your priest or spiritual director, who will be able to help you because he knows who you are and how to help you. Asking anonymous persons on the internet for advice they do not know how to give will not help you.
No. Only make personal vows on the advice of your pastor.
Yes, it would be what is called a rash promise/vow. Confess the sin the next time you go to confession and ask the priest if you can been dispensed, you should also tell him why you made the promise out of fear.