please help! 21 month old still waking at 12 and 4

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My toddler is driving us over the edge. She wakes every night at around 12 or 1 or 2. I used to nurse her at night but don't anymore. Now dh or I pat her/ give her a few ducks of a bottle. Last night I was sick feeding a toDo let at night so she complained/cried for five mins. The I gave her a quick pat and reassurance and she fell asleep. She still woke at 4:30 . dh patted and soothed her until 5. Then she came into our bed to nurse/ sleep until 6:30. This is Ok but is the nursing at 5 an causing the nighttime waking? How can we help her to fall asleep on her own in the night? We are on the edge of exhaustion. Some nights it has taken two hours of patting to get her back to sleep.