It sounds like you've set your router up as the primary (and only) DNS server on the network, and configured the router's upstream DNS server as the Pi-Hole. Which will work fine, but as you've noted you'll only see traffic from the router ('cos all your clients are asking the router, then the router's asking the Pi-Hole.) A better way is to configure the router to give out the Pi-Hole's IP address as the DNS server, rather than its own. If you can configure that on the router, there's no need to move your DHCP service away from it; if you can't, you'll have to shift your DHCP service. Personally, I have my own DHCP servers outwith the router - but they're not running in Pi-Hole, they're a pooled pair of ISC DHCP.