Pumping

I want to start pumping before I go back to work and only nurse at night. My questions are-when should I start this and will it hurt my supply? Baby already takes a bottle no problem but I worry about not giving him breast any time he wants. Will this confuse him, hurt him? I’ve never successfully breastfed before so these may sound like silly questions but I honestly don’t know. I definitely don’t want to lose my supply but I’d rather get him used to it if that’s what needs to be done then wait until I go back to work and there be issues.