(See the best response by Lummox JR.)
I was able to port forward properly and I went to to see if the port was open and it says "SUCCESS" but whenever I try to join a game from another computer it still doesn't. I have Window 10 with Windows Firewall, Malwarebytes, and Bitdefender Antivirus FREE Edition. I tried turning all of these off and still I am unable to connect... this doesn't make any sense to me.

If anyone can help, I'd greatly appreciate it. If you guys need any more info, I'll gladly give it
Best response
It's possible your router is looping back the connection incorrectly. Some routers handle connecting to your external IP address a little weird.
So does this mean other people can join, just not those that are connected to my router? Or does it handle the connecting the same way?

And what can I do to solve this issue? I've been stuck on this for a while and its frustrating. Maybe there are other alternatives to host? Idk any off the top of my head