Re: Sleep Issues since returning to work
I hate to say it, but this sounds very normal to me. At this age many babies, including those who were "good" sleepers, return to a pattern of frequent night-waking. Developmental milestones (like rolling, then crawling and standing), teething (probably well under way by 4 months), and hunger can all conspire to create frequent wake-ups.
Co-sleeping will probably help, if you are not already doing it. In addition, I suggest taking a look at Elizabeth Pantley's book "The No-Cry Sleep Solution" for a primer on normal infant sleep and some gentle, breastfeeding-friendly ways to get babies to sleep longer and more independently.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"