Help!

Kaitlyn

So my daughter is 7 months old we breastfeed only but I just got my period a week ago and my supply has dropped a lot. I literally just pumped for 20 minutes at work and only got 3oz. Any suggestions on how to help? Should I get some formula for her while I’m at work? I really don’t know what to do. I don’t have any supply saved up. All I have for my 8/9 hour shift tomorrow is the 3oz.