Sudden dip in milk supply

Hey all, I’m 17 weeks PP and all of a sudden it’s like i’ve stopped producing milk, my boobs aren’t replenishing. I had a bad week last week with eating and water but I’ve been drinking 3+ litres of water distance then and eating very protein rush and nutrient dense foods but my boobs still feel empty. My baby is getting something but she’s not been producing as many wet nappies which tells me she’s not getting enough. I don’t know what to do really don’t want to use formula although I may have to while i figure out what’s up with my milk. Any advice would be really helpful xxx