Pumping supply

I have 6 month old twin boys. Since returning to work about a month ago my milk supply has dropped. I have been pumping about every 3 hours at work and nursing them before bed. They get about 12 ounces each of breast milk a day and the rest is formula. I am so exhausted plus I have a 5 year old that needs my attention too. Since my supply dropped so much by the time I get home my breasts are so empty the babies need a bottle to fill them up. My question is , is this amount of breast milk enough for any benefit! Does anyone have any similar situations they could share? I'm considering completely stopping, but do I have any hope to raise my supply since it has dropped so much? They are eating so much now I would have to make about 50 ounces a day, and it seems nearly impossible to do this.