"I've been happy with my form, although I haven't had the best of luck with my finishing so far," Fagan told Bristol City's official website.
"There's a great bunch of lads here and I was surprised by the volume of the support the team received away at Blackpool.
"I know Birmingham are monitoring my progress. If they are ready to extend my loan and Bristol City want me to stay, then there won't be a problem."
Fagan's one month deal with the Robins expires after their game with Notts County on Saturday, 15th February.