Breastfeeding experience (During maternity leave)

I didn't breastfeed Pie for long... it was around 2 months only. Reason being, I was into depression thinking that I've not enough supply, not much support from family and also did not read enough about breastfeeding. All in, I could say Pie is 50% breastfed. I also made my first huge mistake when I allowed Pie to be formula-fed right at the hospital, thinking that she could be hungry and that I didn't have enough milk for her to drink. I was nagged by the staff nurse when she found out what happened, which made me more depressed.

Therefore, for Pea, I tried to change my thinking and attitude. My colleague gave me a photostated copy of a breastfeeding book, which I read (twice) months before my due date. At the same time, I went into multiple breastfeeding sites, to enhance my knowledge. I dare not say that Pea is 100% breastfed (she is about 90% breastfed); she has drank formula a number of times, especially once at night to let her sleep longer, but I know she prefers my milk than the formula ones (which motivated me to breastfeed her and express milk for her to drink). But at the same time, I do tire myself out because of the same reason. Now, I have some EBM stored in the freezer and fridge, which I bring out to use twice in a day, once during dinner time (if she disturbs my dinner) and once when hubby feeds her at night... The other times, she is fed directly (which means I wake up around 4 am and 7 am to feed her... luckily now she drinks around 10 mins - yeah I do time her - thus it wasn't that long... but then after she has drank, I will expressed the balance out for storage). I only wonder when I start work, would I be that hardworking (esp. the night shift), would I be able to sacrifice my sleep for feeding her and expressing her, would I have enough sleep to last me the next day in the office, esp. in my current position ? Time will tell...