Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...

As you can see by the size of this forum and all the personal stories that we humans are greatly flawed and selfish. Adultery is one of the most harmful things you can do to someone you claimed to have loved, yet it occurs every day in a large percentage of marriages.
In some cases the person who cheats can't even grasp or care about the pain they are causing and this is a even greater shame.
I'm glad that you are starting to move forward in your life without your ex. Trust in God's strength as during these times we have little strength left to spare trying to get through life/family in general.