Im so freaking sad

Our son is a month old today, Im finding myself crying and really anxious about going back to work in 3 weeks. This is our last baby, I only got to take 8 weeks off work where as with our other 3 kids i ve always been able to take the full 12 weeks off, I'm freaking out about not pumping enough and being away from him for 12 hrs 3 days a week. I know I'll manage to get through it but I'm just super sad, I don't think I was this upset with even my 1st when I had to go back to work.