Piggy's biggest conflict in the Lord of the Flies comes from his struggle to form friendships and positive relationships with the other boys. The other boys view Piggy as a nuisance; his different physical characteristics like his use of glasses and overweight physique make him an outcast among the other boys and more importantly an easy target for their cruel jokes and teasing. Jack Merridew singles Piggy out in their first meeting by calling him "Fatty." Moreover, Piggy's intellect and propensity to make speeches make Piggy an undesirable companion; the other boys really do not appreciate listening to his long-winded ideas or lofty speeches, however correct he may be at times.
Piggy also struggles physically; his asthma and short-sightedness impair his ability to adapt to island life in the easy way that some of the other boys have. He is physically unable to keep up with many of their activities, from climbing the mountain to swimming in the lagoon. When his glasses break, Piggy is even more unable to cope, only being able to see out of one eye, and when Jack steals the glasses, he effectively renders Piggy blind.
Piggy is overweight, he can't swim, and he has asthma. So, he's not physically equipped to be a hunter or to do much physical work. And he's not able to defend himself in a fight. He also needs glasses to be able to see. At first, his glasses give him an indirect purpose because Ralph uses them to ignite the fire. But once Jack steals the glasses, Piggy is relatively helpless.
Piggy also has the disadvantage of being nicknamed "Piggy." Because of this, because of his size, and because he is more intellectual than the others, he is often mocked and dismissed as a nerd.
Despite all of this, Piggy is loyal to Ralph and brave enough to speak his mind and stand up to Jack. His loyalty and thoughtfulness are admirable qualities and they would be useful if the boys had remained loyal to Ralph and put his ideas into practice. But as most of the boys descended into less civilized ways by following Jack, the voices of reason (Ralph, Piggy, and Simon) essentially became unheard. In other words, as time went on, Piggy's fate grew more perilous because he was a thoughtful person in an increasingly thoughtless environment.
Piggy is well aware of how the others perceive him and he's aware that Jack and his followers see Piggy as an annoyance or a target, rather than a thoughtful kid who is only trying to establish order for their survival. Speaking to Ralph about Jack at the end of Chapter 5, Piggy says:
I been in bed so much I done some thinking. I know about people. I know about me. And him. He can't hurt you: but if you stand out of the way he'd hurt the next thing. And that's me.