Breastfeeding... Supply question?

I have a month old baby girl n hav t go back to work tonight, if I don't pump or nurse for 7 hours, what will it do to my milk supply? I really want t keep breastfeeding while working, and although everyone at work is very supportive, there's nowhere private for me to go and pump. And using the bathroom is not an option, it's pretty awful in there... I'm afraid when I get home and feed her, she won't have any milk :-(