Ronniesteers, I have witnessed the same behavior from my wife over the past year. she is BP and currently trying to find the right combo of meds.
we also have a daughter 5 and a son 3. I have herd her say the same things you have said. that she hates herself for the way she is with the kids. she says she is a bad mother. she is not, infact befor she flipped (not trying to insult anyone) She was the one that everyone wanted to leave their kids with. People were always telling her to open a day care because she was so patient and good with kids. I'm glad now that she didn't I would be running it now

. Anyway kids can be very stressful, and I don't think someone with BP is able to cope at times. I see with my wife that the less stress in life the better she gets, but through in a slight amount of stress, like the kids acting up, and watch out!
it is good though that you recognize it and want to fix it.
Remember, kids learn their behaviour from thier parents.