Your router needs to let the traffic in.
The router is running a NAT (Network Address Translation) router and firewall. This is a good thing. It means that if one of your devices wants to call out, then the router makes it look like it is the router that is calling. From the outside all of your devices look like one, and they all share your "external IP address", so you only need one of them however many devices you have. That's a good thing because those are in very limited supply now. Part of the firewall thing is that it stops any outside device connecting to any internal device. So a hacker can't login to your Pi or your phone and so forth. But you are going to have to forego a little of that security to allow anyone outside to see your website.
What you need to do is to tell the router that any traffic coming in from the outside on a particular protocol and port should be sent to a particular port on the Pi.
The HTTP protocol used by websites is a TCP protocol and it is usually on port 80. You can change that port number and get a little more security. Say you choose port 8000. So you tell your router to forward all traffic it gets on TCP port 8000 to port 80 on your Pi's static IP address. All routers are different so I can't tell you how to do that. Look in your router's configuration web pages for "Port Forwarding". It maybe under an "Advanced" tab; for mine I need to select Advanced twice before I get to it.
Then to see your Pi's website from outside your network, you need to connect to
http://68.148.183.154:8000/
Note though that once you've done this anyone from outside can send traffic to your Pi, albeit only web traffic. If there is a bug in your webserver though a hacker can exploit it to get normal login access to your Pi, and from there of course, they can access all of the other devices on your network. It is vital that you keep your Pi patched, especially those patches that are related to networking and the webserver.