Why is my 'What is my IP' tool showing wrong public IP?

I'm completely stuck trying to debug my "What is my IP Address" tool! I just launched this simple web tool, which is designed to display the user's current public IP, but it keeps returning an incorrect internal or proxy IP. The core functionality relies on accurate client IP detection, and right now, it's consistently showing an IP like 10.x.x.x or 172.x.x.x, or even a datacenter proxy IP, instead of the user's actual external IP. This problem is happening across different networks and browsers, and it's incredibly frustrating.

I've spent hours troubleshooting. I've thoroughly checked X-Forwarded-For and other relevant HTTP headers, thinking it might be a proxy issue. I've also verified server-side logging, but nothing obvious is jumping out. To confirm it's not a network-wide problem, I even tested with various third-party IP lookup APIs, and they all correctly return the actual public IP, which makes my tool's failure even more puzzling. Here's a dummy console output illustrating the discrepancy:

// Expected:
// Client IP: 203.0.113.45 (Actual public IP)

// Actual output from my tool:
// Client IP: 10.0.0.5 (Internal/Proxy IP)
// Or sometimes: 192.168.1.100 (Internal IP)
// Or: 172.16.0.1 (VPN/Proxy IP)

I'm completely out of ideas and frankly, this is breaking the core functionality of the tool. I urgently need an expert to point me in the right direction, as I'm completely stuck. Any insights would be massively appreciated! Waiting for an expert reply.