@Ashley Zhang, sounds terrible. Really sorry you’re deal with that.
You can always file a claim on your insurance policy. If your local State Farm agent resists, call the State Farm claim number directly (just google it). Then a company adjuster will look at your policy and decide if what happened is covered. Could filing a claim have a negative effect on price even if it doesn't pay out? Unfortunately, yes. At the same time, filing a claim is the only way you can truly hear the company's assessment of the scenario.
Based on what you've said, standard insurance policies may not include coverage. The insurance adjuster is going to look at the source of the damage and compare that to what your policy covers. The possibilities seem to be: sewer leak, flies, water erosion. Let's address each separately:
SEWER LINE LEAK:
If you have "Service Line Coverage" or "Utility Line Coverage" that would likely apply to this scenario. If you have "Water Back Up Coverage" that may apply as well. If you don't have either it's hard to see where a standard policy would address this.
FLIES:
Standard policies have an exclusion for damage caused by, "birds, vermin, rodents, or insects". Thinking insects would be the deal here. Having noted that exclusion, it doesn't seem like the damage was caused by insects. They are a result of something else.
WATER EROSION:
Inside your home, say a toilet valve leaks. The resulting water damage is often covered even though replacing the value that leaked is not. I think there's an argument to be made that this is water damage as the result of a system failure. The issue with this argument may be the fact that it's an external failure (it's not in your house).
Bottom Line: It may be worth filing and seeing where the insurance adjuster goes. I can see a lot of ways this ends up not being covered but there are a few avenues, depending on your policy, where it could be. If you have Service Line Coverage, definitely file the claim.
Hope this was helpful. Feel free to reach out if you need more thoughts.