OK I have not read any other post apart from your original one, so wanted to respond with my immediate feelings.
This is me totally, 100% to the letter.
I adore my DT's, die for them like you say, could stand watching them sleep forever, catch my breath when they smile - obsessed you might say!
Then one will whinge at me 'mummy, i want grapes, mummy, i want this, i want that'. I start to feel all hot, sick almost and then snap at the next comment to come out of their mouths.......
I blamed dh, i blamed them, i blamed life.....then i blamed me. I went to docs, explained as much as i could (don't know about you but I find it hard to express the depth of my emotions when i'm actually having a good day), she put me on anti d's and put me forward for councelling. The change was AMAZING! That was last year. I am off the pills now (through my own choice), but have booked an appointment with HV to see if my issues are that i have particularly badly behaved children (which i doubt) and also i will eventually start seeing a councellor.
A lot of people are very anti pills as a solution and i agree, they are not a solution. They actually took the red mist of anger and despair away and allowed me to see life how it should be lived and showed me how much i could ENJOY being a parent. Coming off them was a risk, but I feel fine MOST of the time, i still have my moments which is why i want to talk things through with a professional.
My message to you is you are not alone, you are not failing your kids, you do deserve them, but there 'could' be a wee chemical imbalance which isn't allowing you to see the true joy that kids bring. If pills are not your thing, you really do need to find some 'ME' time. Do you have family close by? perhaps get them to baby sit while you go to the gym or swimming or go out for a glass of wine with a friend? Increased exercise can increase you seratonin levels naturally without the help of pills.
the main point is TALK to someone in RL as well as on here, believe me as soon as it's off your chest you will feel human again, rather than an emotional freak!
take care, hope i haven;t repeated what everyone else has said!