Dear Laurie,
I'm glad you are now in a safer, happier place. Most of all, it's great you're with someone whom you can love and who loves you back.
In this article on
IVF and Tubral Procedures it says "In vitro fertilization (IVF) is the combining of a woman's eggs and a man's sperm in a laboratory. The resulting embryo or embryos are then transferred into the uterus. Your doctor can use your eggs and sperm for IVF or donor eggs or sperm if necessary."
So I believe the answer is a cautious "Yes." First, you would need to talk with a gay-friendly reproductive expert, and discuss whether or not you're a good candidate, and get your partner checked out, too.
What you're asking for would require trying to "synch" up both your cycles and then to be able to fertilize both her eggs and your own with the same donor. Then the eggs would in theory (if your doctor clears you) be implanted in you. If all went just right, you would have twins who were half-siblings (if you chose the same donor father).
It might be less expensive to try something like IUI (Intra-Uterine Insemination) and have your child. Then for the next pregnancy, use IVF and you could be the surrogate for your partner's child if she doesn't want to be pregnant. As long as you both use the same donor, the resulting children will still be half-siblings.
The least expensive way would be for you both to use a sperm bank, get inseminated by the same donor, and both of you carry naturally. This way you save the hefty costs involved in IVF, IUI, and other fertility treatments.
Make sure to look at the legal side of things. Some states/countries do not allow same-sex partners to adopt their partner's child. You also want to discuss what happens if you two should break up, one of you should die, etc. Not pleasant topics, but ones that need to be discussed with a lawyer to make sure your childrens' best interests are protected.
Also, if you don't use a sperm bank, you'll need to draw up papers that legally define the male donor's position in the children's lives. Otherwise, you could have "daddy" suing you for custody down the road.
Best wishes and write back when you get a chance,
Byroney