It sounds like you're doing good, if you detest sit-ups as much as I do, there is an alternative. sit back in a straight chair, and pull in your stomach muscles and hold for a count of 20, then slowly release-don't forget to breathe.
Something to use when you're in front of the computer and need to sit back and take a break. repeat 5-10 times a day. and because no one knows you're doing it(how many people stare at bellies anyhow) you can also do it standing up, waiting for a bus, or to cross a street with your bike, just straighten up and pull in those muscles-also very low impact, so you won't get achy muscles.

Lois