When my mom had hernia surgery that would require mesh, the surgeon said it was normal to have a fluid accumulation during healing. He said the fluid would be drained at the appropriate time, and it did not mean there was an infection at all. Just routine follow-up because the mesh causes a backup of fluid. Is that the problem?
I have First Assisted on hundreds of umbilical hernia repairs, with and without mesh. It certainly sounds like a infection to me. I would tell my Doc "humor me" and put me on antibiotics! What's it going to hurt? Best wishes! jd1963