Maggiesmommy - I hope you got the reply to my email but i'll post it here for you also.
It is awful to doubt yourself, especially when you have a newborn who is totally dependent on you. I have been there and understand! My LO took all her naps in the swing until she was almost 4mos old, so I know a lot about accidental parenting. Then I found Tracy's book - do you have the new book? It is an excellent resource for learning how to put your LO on a flexible routine, how to teach sleep and also techniques on how to un-do the accidental parenting you have been doing.
So that I know where you are starting from, can you tell me if you have read the book?
If you are really ready to make some changes then stopping the nurse to sleep and feed on demand is a great place to start.
Second step would be to put your LO on a flexible 3hr EASY routine - which stands for Eat, Activity, Sleep, You time. No nursing to sleep.
Regarding the 45min naps -
point 1 - this is very normal at this age and when my LO started them also. The reason is from 0-3 months babies work on organizing their night sleep. From 3-6 they work on organizing their day sleep. When she wakes at the first 45min mark she has completed 1 sleep cycle. Also there are specific partial awakenings in an infants sleep cycle-- 10 min., 20 min and 40 min. mark. So it sounds like she is having trouble getting past the first cycle and transitioning from the partial awakening after that.
point 2 - Keep doing shh/pat to get her back to sleep and keep trying until is it time for her next feed (approx 40min). Then get her up, feed and put her back down for a sleep right away - see if this helps. It maybe that she is overtired and over-stimulated which can make it difficult for a newborn/young infant to fall asleep/stay asleep. That's why an infant will sleep for only 10 min, 20 min at a time.
You said you were on a 3hr schedule, how long is she wake before starting her next nap?
Third step is to start teaching her to fall asleep independently and in her crib.
Hang in there - we can support you if you are really ready to make changes.