An exciting but scary time misbec!!
90mls is a lot for a tiny bub like yours hun so don't worry it should be more like 60mls! So she is doing well. Her tummy is only the size of her fist if that. I had not so great boobs for feeding too. DD was on 60mls of formula every four hours when we left hossy at 7 days. We were trying to flush her jaundice before my supply was enough that I could express full time. Around 10 or 12 days we upped it to 80mls

She will work out night from day soon enough on her own it can take a little while. One thing I did was expose my DD to light during the day and made sure at when it got dark at night we kept it darkish in the house but really not much you can do.