Installed CWM/TWRP but it isn't installed when booting to recovery mode

I have an LG G2-D800 running 4.4.2 KitKat and it is rooted using an app called Stump Root. I have been trying to flash a new ROM onto it and every time it boots into recovery, it boots into the android recovery, even though I have flashed it using Clockwork Mod and TWRP Manager. Can anyone help with this and suggest good ROMs to flash to it?