I work from home and keep my 4-month old daughter as well. I have experienced some of the same issues. I have found that if I need to get things done having her in the room with me helps because she can see me, even if I'm on the laptop working. Even still, I find it hard to get things done for any length of time because it isn't long before she's fussing.
While I am sure a carrier would be a good idea sometimes, I am a firm believer in allowing the child to learn to be independent (within reason of course) even at this young of an age. Of course, always go to her to soothe her and let her know you are there, but let her learn to soothe and entertain herself with toys, mirrors, etc. Sing and talk to her so she can hear your voice while sitting near her.
It is possible that she is bored. Babies at this age have about a 15-20 minute attention span, so she might just need something to engage her. I know many parents think television is bad for kids this age, but I used to put on a Baby Einstein video for my first daughter starting at about 5-mos old, and that half hour allowed me to fold the laundry, make dinner, answer a few emails, etc. Plus, she loved the colors and movement and the music was relaxing to us both. Also a change of scenery might help too. A walk outside (once it warms up if you live in a cold area), a ride in the car, a walk around the mall or a trip to the grocery store might help. As a new mom, your hours can easily turn into days, months and you need the change of scenery as much as your baby does!
It is so easy to get overwhelmed as a new mom (or even as a second-time mom, like me). As she gets older, she will require more and more of your attention. My best advice (which I wish I would have followed when I was a new mom) is to let the house go, let Dad make dinner or order take out and enjoy every minute you get with your baby. I went back to work after my first and now I work at home so I can be here for my second baby. It is hard and really frustrating at times when you feel like nothing you can do will appease them, but the first year goes by so fast and before you know it they are turning three and you'll find yourself dealing with a whole different animal!!!