My baby is 7w5d.she used to drink 4-5oz/3hr.i did change e bottle nipple to size 2.since 3days ago,she will only tk 2oz/4hr.her body temp is normal.

Over feeding? : 2 -3oz is more than enough formula for a 2mo old baby, but 4-5oz is way too much for a baby this young. I suggest you discuss feeding amounts with your baby's doctor - much of this has to do with the baby's size, but clearly, 4-5 oz is not healthy, and should not be given at that volume until the baby is at least 3 or 4 months old. See your Pediatrician for more advice

Dehydration/wt loss: Have you tried to change the nipple back to the previous size? No breastfeeding? It is very healthy for babies to prevent disease with your antibodies in it. If she will not take in the amount before the nipple change after changing it back, need to call Pediatrician. If less than 5 wet diapers/ day to ER. For 50% weight of girls, she is not taking in enough fluids. Dehydration is a concern.