Cannot Join My Dedicated Server

Pretty much I have a problem where if I define my IP as which is my computers local IP (my routers IP being and internet IP being other people will be able to join using my internet IP but I cannot join my own server on the same computer i’m hosting it on. I’ve talked to 3 people who host dedicated servers on gmod and they can all join their own servers on the same PC they host from(except one who uses server boxes)

I use srcds, I have port forwarded correctly and done almost everything right seeing that other people can join my server. I also know that joining your own server makes it lag quite a lot and decreases its performance. My server is a private server for only me and a few friends to mess around on. It’s essentially a build server with many addons where I can show my friends cool contraptions and muck around with the addons, so really I don’t care too much about performance so long as it works.

So I just really want to know what I have to do for the server to allow me to play on it.
Oh and by I can’t join I mean I can find it in LAN but when I join it just fails connecting after 4 retries.

Any help is appreciated.