There could be several different factors here. It might be easier to talk to someone on the phone, who can ask you questions about your situation and narrow down a solution that would work for you. www.lalecheleague.org has a link to finding leaders near you--you can call at any time, and it's free! If you can't reach the first one you try, or if you feel she wasn't helpful, call another one.
One leader who has personal experience with working and pumping is Dawn in the Central Gwinnett group--you can find her contact info on the website.
Some moms don't let down well to a pump, and can never get as much out that way as the baby would be able to get directly. There are some things that might help with that--some mothers find that it helps to sit down and relax for a minute, and visualize their baby; other things that can help are looking at a photograph, listening to a recording of your baby's voice, and even smelling a blanket or item of clothing your baby has worn.
I know it can be hard to find the time to pump when you are on the job--but it may also help if you keep pumping for a minute or two after nothing seems to be coming out. Sometimes that can help with the milk supply. While your breasts are never really empty (they are always producing milk) thoroughly "emptying" the breasts until nothing is coming out for a few minutes helps to stimulate milk production.
Here's another thing to consider. You said that you are feeding her twice a day; something that can make a big difference would be to increase the amount of time you spend nursing in the evening, night, and morning when you are home.
Some mothers find that when they go back to work, their babies don't take as much milk during the day (either because the baby doesn't take much from a bottle, or because she can't pump as much). Many of them have found that they can make up for this by nursing often when they are home at night. Babies naturally tend to "cluster nurse"--they go for longer periods without nursing (generally at night, or so we tend to prefer!) and then nurse more often at other times (during the day.) Working moms often find that this pattern gets reversed--their babies do lots of nursing in the evening and night to make up for not getting as much in the daytime.
This may sound unworkable, since of course you need to sleep! If you are open to the idea, I know quite a few moms who keep the baby next to them in bed, and don't even really wake up when the baby nurses. This has been a lifesaver for some of the working moms I know. If you are interested in trying it, there are safety guidelines you should follow:
Even if that option doesn't work out for you (it works well for some, but isn't for everyone), you can try nursing the baby at the daycare when you get her, and then as often as she's interested in the evening before bed, and then as soon as she wakes up, and again at the daycare before you leave.
Have you ever tried using a sling? When I had my second child, I needed to be mobile and have free hands since I had an older child (and a house) to take care of. I loved the mayawrap (www.mayawrap.com). It takes a little practice, but you can learn to nurse in it, and that lets you multitask in the evenings so you aren't stuck in a chair when you nurse. If you get one and need help figuring it out, your local LLL group can help you. Some groups have evening meetings (including the Central Gwinnett group).
As others have said, you should be careful about dieting right now. It is possible to watch your diet and safely lose weight while nursing, but restricting your intake too much could contribute to a supply problem.
I want to correct one thing that someone else posted--while it's true that you should eat as healthy a diet as you can, it isn't true that your milk will be poor quality of your diet isn't perfect. When women eat a poor diet, they still make nutritious milk, better than formula--the problem is that they rob their own bodies of needed nutrients. Your body will make the milk a priority and cheat itself. A healthy diet will benefit you, and can make your milk even better--but fortunately a bad diet doesn't mean that your milk will be bad. Human milk often looks like skim milk--it varies at different times and with different mothers. The milk that comes out first is more watery, and the creamy milk comes out at the end of a feeding or pumping.