Where's Waldo?

Alright, I know what my problem is, I just need to find the source of it: on the final line of check() (the bottom function), I call addVal(). Upon stepping into addVal(), I find that *root = fp. Here's my code, I hope someone can help me find my error.
P.S. before the function call to addVal(), root is fine.

PRIMER.C

#include <stdio.h>
#include <stdlib.h>
#include "primer.h"

void main(){
struct node** primes;
int current;

FILE* fp;
fp = fopen("primes.txt", "r+");
primes = NULL;
current = 3;

if(fp == NULL){
printf("No saved progress found.\nTime to kick *** and take primes.\n");
fp = fopen("primes.txt", "w+");
primes = addVal(fp, 2, primes);
}
else{
printf("Saved progress found.\nLoading file to continue previous progress.\n");
initList(primes, fp);
}

while(1){
primes = check(current, primes, fp);
current += 2;
}

fclose(fp);
return;
}

//add a value to both the array and the file
struct node** addVal(FILE* fp, int value, struct node** root){
fprintf(fp, "%d\n", value);
return insert(value, root);
}

//insert a value into the list
struct node** insert(int value, struct node** root){
struct node* newNode;
newNode = (struct node *)malloc(sizeof(struct node));
newNode->val = value;
newNode->next = NULL;
if(root == NULL){
root = &newNode;
}else if(*root == NULL){
*root = newNode;
}else{
newNode->next = *root;
*root = newNode;
}
return root;
}

//set up the prime list and read all primes from file to the list
struct node** initList(struct node** root, FILE* fp){
int next;
int i;

while(!EOF){
fscanf(fp, "%d", &next);
root = insert(next, root);
}
return root;
}

//check to see if the integer is a prime. If so, add it to the file and list.
struct node** check(int value, struct node** root, FILE* fp){
struct node* currentNode;
currentNode = NULL;
if(root == NULL || *root == NULL){
printf("error: NULL pointer where there can't be one. in check method\n");
//exit(0);
}else{
currentNode = *root;
}

while(currentNode != NULL){
if(value%(currentNode->val) == 0){
return root;
}
currentNode = currentNode->next;
}

return addVal(fp, value, root);
}



PRIMER.H

struct node** addVal(FILE* fp, int value, struct node** root);
struct node** insert(int value, struct node** root);
struct node** initList(struct node** root, FILE* fp);
/*function: check()
*precondition: root is nonempty
*/
struct node** check(int value, struct node** root, FILE* fp);
struct node{
int val;
struct node* next;
};