crying baby

Hey moms! I have an 8 day old newborn and all she does is scream! I was strictly breastfeeding her, but she wasn't getting enough food. So I started supplementing with 2 oz of gentle ease formula at every feeding (every 2-3 hours) she's pretty gassy most of the time. I just don't know what to do to ease her crying. We walk with her, lightly bounce on the birthing ball, sing, talk, dance. Try to nap! She hardly sleeps. It's killing this mama! I'm starting to regret having a baby because it's just so hard! I'm exhausted and running out of ideas. Anyone been through this and have any suggestions? How long does this stage last? Anything will help. Feeling like a bad mom. 😢