Breastfeeding & in tears

I’m 11 pp and I made the mistake of not pumping till about a week ago. I’m going back to work so I need to pump. My daughter has gained weight and is going great. But now I feel like I can’t keep up with her feedings and pumping. How many times a day am I suppose to pump? Is it normal that sometimes when I pump I’ll let 4-6 ounces (from both combined) and sometimes I just get a drop! Help please I’m getting so frustrated and feel like I’m failing