Supplementing?

My daughter is almost 4 months old an has been EBF. She will be starting day care a week before she turns 5 months old. I am slowly starting back at work (private practice therapist), only 1-2 days a week for a couple hours. She is with my Mom or Dad on their off days. I can pump enough to get a bottle for that amount of time. However, I am worried when I go back full time that I will not be able to keep up with how much she eats. Even 1st in the morning I cab only get maybe 3 oz total! I am considering supplementing with formula. I have also had problems with her having very bad gas pains, despite changing my diet, so hoping it could help things. Can anyone suggest a good formula to transition her to? And please before any judgemental comments...this is a very tough choice as I wanted to breastfeed until at minimum 6 months. I have tried a hospital grade pump, smaller shield size, fenugrek pills, power pumping and drinking water like a horse. I have a frozen stash of about 60oz. Praying to make it 6 months EBF. But, need advice if I can't.