do her eyes look sunken in? dehydrated? please help!

Hey everyone, so at my daughters 2 month appointment, doctor said she’s not gaining as much weight as she’d like her to see. She didn’t seem super concerned but she said to just try to feed baby more. My daughter’s on formula now due to health complications on my side that we’re making it hard for me to continue to breastfeed her. Doctor said she should be drinking anywhere from 4-6 oz each feeding ( she said typically every 3 hours ) but in all honesty, I think my daughters a picky eater. There’s times where she’ll eat 5 oz, then 2 then 3 then 4, it varies. I’ve tried to burp her in between then continue but she’ll stop most of the time. At night she goes maybe 4 hours without waking up for a feeding and when I try to wake her she just pushes the bottle away. She’s still having a good amount of wet diapers although Now I’m worried she’s not eating enough and that she’ll become dehydrated. Any tips? Please help! I’m completely stressed out!