Hi Austin,
Try below configuration.
interface FastEthernet0.5
encapsulation dot1Q 5 native
no ip route-cache
bridge-group 1
no bridge-group 1 source-learning
bridge-group 1 spanning-disabled
interface BVI1
ip address 192.168.5.228 255.255.255.0
no ip route-cache
Your switch port should be trunk with vlan 5 as native vlan. Also you don't need helper address on BVI interface and helper address should be on the L3 interface .i.e the default gateway interface of the AP.
Hope that helps.
Regards
Najaf