How do you forget betrayal from a spouse and learn to forgive. Or learn to trust..?

I don't know if he cheated but i read every message he wrote to several girls and I am clueless to what else was going on behind my back and i believe there is more, i want to know how to just move on from this but its hard. He swears he never cheated but i don't believe him. I want to move on and just forgive for the sake of my son, our son.