DHCP server does not necessarily mean default gateway.
If you are not using the DHCP server on your router, you need to either
- set up another DHCP server on another computer or something else somewhere
- assign IPs manually to all devices
Clients reach the DHCP server through broadcasts, i.e. traffic that is set to reach all nodes on your network. So nothing needs to know the IP of your DHCP server as long as the DHCP server is listening on something that is in the same subnet as the rest of your network.
Your DHCP server should be configured to hand out the router's IP as the default gateway.
Per your situation, if all you did was disable the DHCP server, the IP of the router probably didn't change and you can still use the same IP to get to it. If you do NOT have a DHCP server elsewhere on your network, try setting your IP to 192.168.X.44 subnet mask 255.255.255.0 - X is probably going to be 0 or 1 - then you can probably reach your router at 192.168.X.1 or 192.168.X.254.