What is the main conflict in The World According to Garp by John Irving?

There isn't just one conflict in the story, rather than conflicts in life that surround different characters. Garps mother is a radically independent nurse who conceives him by taking advantage of a brain-damaged soldier. His best friend is a transsexual who was formerly a tight end for the Philadelphia Eagles. Garp struggles vainly to protect the people he loves. His life is both hilarious and ultimately tragic.