The first question I will like to ask you is, do you love him? If your answer is yes, then you need to pray to God for strength against temptations that will lead you to cheat on him (again). During our moments of weaknesses, that is, when we feel lonely, down or angry, our mind becomes a "temptation playground" and in such moments, it's eminent that you fight off any thoughts that would lead you into temptation, by taking them captive and making them obedient to Christ as Paul stated in 2 Corinthians 10:5, or as Jesus did in Luke 4:1-13. Thank you...