Hi F.,
First of all, congratulations on nursing and pumping! Your committment to your babie's health and development is inspiring.
I'm a training laction consultant and if I had a nickle for every time I heard a mom say that she's worried about her milk supply...
The truth is that at this point our milk production does not diminish, it becomes perfectly balanced. That means that you're no longer producing more milk than she needs, and that your body and your baby are in a synchronized rythm. You produce, she drains. Pumping becomes more difficult because your body knows the difference between her and the pump. Your body knows it doesn't have to save up the milk for her during pumping times and it isn't going to let as much down as when she suckles, either. Do keep pumping, though, as the nipple stimulation and draining are important. You can also try a different size shield on your pump.
You can try manual expression instead of the pump. It is more work but some women have better results manually.
Please do not think that you're not making enough for your baby just because you're not getting what you expect from a pump. I was never able to get more than 3-4 oz. out with a pump after the first two months. But my babies were nursed exclusively until 6 months and I continued to nurse for at least one more year for each of them.
If your baby is growing, wetting diapers and generally thriving then your breasts are producing perfect amounts of milk.
If you have started her on solids then your milk supply will be a little lower, again just because of your body being perfectly synched with her needs.
If you need to increase your milk supply you can lie around naked with her in bed for the weekend, touching skin as much as possible and having your husband wait on you. Drink as much water in bed as you possibly can and your milk supply will go up within 24 hours.
Good luck and congratulations on being a great mom!