Please help. My 5 month old is losing weight

I have tried literally everything, I'm wracking my brain constantly about wth I'm supposed to do. My 5 month old girl has always been EBF, always had a good latch etc. However for the last month no matter how much I eat or what I do, my supply just keeps dropping and dropping. She's now in the 5th percentile for weight when she used to be in the 75th. I can't pump enough to mix into oatmeal, rice cereal or homemade purees. My pediatrician wants her drinking at least one bottle of formula a day but she's never taken to any nipple or bottle I've found (I've tried every combination under the sun, I went through a basket of different nipples one day) she somewhat likes a transitional sippycup I found and likes to chew on the tip but haaaaates formula. Once she gets a little bit of it in her mouth she looks disgusted and starts swatting me away until it turns into a full blown tantrum. I've tried putting mashed bananas in it to make it sweet and spoon feed it to her, nope. She spits every bit of what i put in back out. I've tried putting it in a syringe, she will gag and throw it up instantly and throw a tantrum. Ive tried 3 different formulas so far. I already have PPA and this is driving me crazy, I feel like she's starving to death in front of me and theres NOTHING I CAN DO. Please someone tell me they've been through this and found a solution.