pain in stomach after eating pain attack morning

i have been prescribed nexium 40 for acid reflux. up until then i had minor reflux after eating certain foods, chocolates sugars, etc late at night. after taking nexium for about 4 weeks i started to get mild burning pains before eating. i continued taking it until one morning i got severe burning pain that made me want to defecate, but nothing was coming. i quit taking it but and the burning somewhat went away, but now i get the same feeling after i eat my first meal especially. i have to eat potato soup and it goes away, but i still don't quite feel like myself. i went back to the dr. and he prescribed sucrafate. another anti acid. it really didn't seem to do much. the other morning after eating pop corn late and drinking a root beer, i woke up at my usual time or so, with stomach pain that slowly got worse until i almost went to the ER. i took a pain pill that i had left over and it took the pain out and i slept for about 2 hours. when i awoke the pain was gone but my stomach was sore. didn't vomit at all. i have been reading about gallstones on this site and wondered if somehow it was a coincidence with the nexium or could this be a side affect?  or should i get tested for stones. or gall disorders. if it is stones, i read somewhere that there's something that can be taken long term that dissolves the stone. any advice is appreciated
john.
ps. i had a kidney stone about 10 years ago. drank tea for years with splenda or stevia with lemon. does that help or hinder the gallbladder?