Totally understand the paranoia feeling! I've had my fistula for over 5 years, and I STILL get anxious when it starts twinging/aching. Some pain is definitely still normal - it may be painful for several weeks, or even months. What you need to watch out for is a big increase in pain that lasts for a longer period of time. It's going to suddenly ache if you pull it wrong or something, but that wouldn't last for days or even hours.
"For this thing I besought the Lord thrice that it depart from me. He said, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities; I take pleasure in infirmities, reproaches, necessities, persecutions, distresses, for when I am weak, then am I strong" 2 Cor