My mummy guilt is always there. I've taken time off, worked part rime, and now full time. Every option has compromises, and I've felt guilty about something no matter what I do.
My wonderful MIL keeps telling me "Do what feels right for you, don't worry about what other people think". Best advice ever. Hard to do though, when you are judging yourself! A friend of mine has a "guilt box" where she writes down all the things she feels mummy guilt about, then puts the worries in the box, and puts the box away. Out of your head, acknowledged but put away. I'm going to try that this year!