Is once a cheater always a cheater true?

My fiance’ and I have been having a lot of problems, One of the big ones is because I have cheated. Emotionally once and physically once. I know that emotionally thing doesn’t make sense. (C) was working 2nd shift and I was working 1st shift at the time. He only introduced me to maybe 3 people when we moved here. I was hanging out with (F) alot. Feelings started to develop. In the end (C) and I decided to work it out. A few months later (J) came to live with us. We’d talked and joked around and one day it went too far. Again (C) and I decided to work thru our relationship. Things have been really tough between us. I have tried so hard to put things back together and he’s obviously leary which i can understand. I need to know will things ever go back to the way they usto be? I need help. I will do anything to make things go back. Any suggestions?