Most affairs are sexually driven.
When someone discusses cheating, what is the first image that comes to mind? Secret texts? Late-night rendezvous? Lying and manipulation? For many the image is of two people who have been overtaken by mutual sexual desire. A cheating spouse is seen as someone who turns away from family love and selfishly seeks the affections of another. That may be one aspect, but it is not the root cause of infidelity.
In reality, most people have affairs for emotional reasons, not sexual ones. Is this you? You felt ignored by your partner. You felt your needs were unimportant. You felt hurt, and even angry, and did not know what to do with these feelings. Once you felt that your spouse did not care about you, you may have found yourself more open to the attentions of others.
When you felt abandoned by your mate, you were able to justify spending time with people who made you feel that you matter. At that point, you were only one small step away from attraction and unfaithfulness.