It isn't easy -- I know from being a work-at-home mom. You're juggling three jobs at once: the paying gig, caring for your baby, and caretaker of the house. And you feel like you're not doing any of them effectively, especially the babycare. You have to trust you're doing the best you can.
You can't spend every second of the day with her, so don't beat yourself up. Make the most of the time you do have together. I schedule a lunch break and a few 20-minute breaks during the day (just like office workers) so that my girls and I can do something together, whether it's sharing a snack or drawing pictures.
When Lila was a baby, I hired a sitter to take her out for an hour every other day. I was amazed at what I could get done -- and how less guilty I felt knowing that she was active and engaged. Guess what? Both of my kids are just fine -- and confident that their mom works hard and loves them all the same.