My 8 month old has started waking up every 3 hours at night

I feel like I have a newborn again. In fact I think I got more sleep when she was a newborn. She is up every three hours and then takes forever to go back to sleep. Also, only takes thirty minute naps during the day. So I'm not getting any asleep. My relationship is going downhill, my health is declining, and I'm losing my mind. What am I doing wrong?? We have a bedtime routine, we try to get her enough naps, I don't understand. When she wakes up she'll only drink 2-4 oz. im going crazy. I literally can't keep doing this. I don't care what I have to do for the sake of my wellbeing I can't keep being up all night. I'm starting to resent my baby. I know it's not her fault but I have started getting sick and dizzy because I get so exhausted And I'm losing weight.