Miller is currently on loan at QPR after an injury-ravaged two years at the Hawthorns.
He said: "I've had a lot of injuries which have stalled my career at West Brom a little and I just needed something to inject a bit of confidence back in my game.
"It was nice to get the phone call from QPR manager Neil Warnock, who is a great guy at a great club, and I couldn't really say 'no'.
"West Brom have got a great squad there, with a new manager (Roy Hodgson) in place since I left.
"But I was happy there and I am happy here - so I'm not sure what will happen this summer."
Miller added: "I'm not really thinking about my long-term future now because I'm just happy to be playing games again.
"I'm not putting any pressure on either club to make a decision and I will be happy to be playing at either club next season."