K.R.
As a self-professed formula snob, I feel your pain and you sound like me just 2 months ago. I work full time and exclusively nursed my daughter. She's my 3rd and last and it was important to me to keep that up. However, I was having to pump 24 ounces a day. She took 4 six ounce bottles!! If I got stuck in a meeting she would be short the next day and then I had to find time at work to pump double to get my supply back up. I stressed myself out about it so badly I'm sure it hurt my supply even more. My daycare kept gently suggesting adding formula in to which I would cry NO!
Well, at 7 months I finally did it and now I'm wondering what took me so long! I should have started at 6 months and saved myself the stress. I give her 3 ounces of formula and 3 ounces of milk in her bottles for daycare. I nurse her in the morning, evenings and throughout the night. She's a happy little baby and I'm not hooked up to the pump all day while I work!
Even with those 12 ounces of formula my daughter at 8 months old has yellow mustardy bf poops so I know she's getting mostly milk but that 12 ounces I add in sure do make us all happy!
Be kind to yourself, you've done good Mama! Formula isn't the devil LOL (that was from my husband when I was whining about it)