What makes my stomach feel like oil and water?

For about a year now my stomach will just start hurting. It almost feels like I have oil and water in it and it just doesnt mix. You know when you were a kid and you would fill a coke bottle with oil and water and it wouldnt mix. That is what my stomach feels like. I dont know if it is acid, heartburn but I cant figure it out. Any help would be greatfully appreciated.