Oh I can totally sympathise - its my easy is it? I've been working 4 days a week (so not quite full time), since DD was 6 months old, and I spent the last semester studying. I will admit, I have plenty of times where I just feel so guilty, but at other times it doesn't seem so bad....DD loves childcare and I do enjoy my work - it doesn't mean that I don't wish I was spending more time with her though.

As for the staying on top of things tips. These are some things we did:
1. On Saturday and Sunday nights we would cook what we call 'two nighters', meaning we had a couple of nights dinner for the week already pre-prepared. The slowcooker with another one or two nighter during the week is also handy.
2. I'd try and do a load of washing at least a couple of times during the week so there wasn't as much to do on the weekends
3. On a good note, the house doesn't get as dirty during the weeks as you are barely ever there! On the weekends DH and I would just try to get stuck into the housework to get it done. My house rarely looks as good as I'd wish, but it's liveable and occasionally we will do a mega clean.

I hope that helps a little.