When should I expect my period to return?

I've been bottle feeding since my son was 5-6 weeks old. I stopped producing milk when he was about 4 weeks, but I let him use me as a pacifier sometimes after that. He was never exclusively fed. We tried everything, but no luck! This is my first baby, and he's 12 weeks old today (born January 13). My hubby and I have had unprotected , so I'm getting worried. We want another baby, just not now! If you bottle-fed your little one, or you fed and supplemented for a short time, when did your period return?