First "proper" post here, so...hello
I'm in a similar situation - I work for my MIL (a lawyer), and we live in the same building from which she operates her firm, so I'm effectively working from home. I've been back at work since my son was about three months old, and it's been pretty hard going. There are so many great advantages to this set-up: I don't have to leave him in childcare, I can continue to breastfeed without the hassle of expressing milk, and I can work reasonably flexible hours to accommodate his needs. However, the downside is that I can never really concentrate 100% on my work, even when he's asleep, and my productivity has really taken a beating as a result. Also, I find I'm just not capable of doing things the way I used to before (I was really good at juggling a whole bunch of tasks at once - nowadays, I'm pretty happy if I can remember my own name before 9am

). Finally, despite constant reassurances from my MIL and FIL, I have enormous guilt feelings about not managing to work as much as I should for the salary I'm on.
Guh. Sorry, I didn't mean to be so negative.
I'm contemplating what to do about the situation now. I want to stay working, but I'm not sure if I can continue to manage full time work and looking after my son. However, I'm reticent about dropping to part time because I'm not sure whether my problems are really because I'm trying to do too much, or just because I need to plan my day better or sort out my priorities, and I'll face the same problems even if I do go part time.
Man, this is hard work, innit?
Anyway...having washed my head in your thread, I wish you good luck with your return to work, and hope that you find a good balance between looking after bub and getting your work done!
ETA: Just wanted to add, feel free to ask anything about my situation - if there's anything out of my experience that can help make yours run smoothly, then I'm very happy to share!