I'm sorry that this is such a struggle for you. I can imagine how upset you are right now because this also happened to a good friend of mine. She did not plan to become pregnant and didn't want children. They used birth control, but at one point she did get pregnant anyway. Her pregnancy was pretty miserable, and she, like you, was very conflicted early on about what to do.
I won't tell you what she did, because it really doesn't matter. What matters is that you make the right choice for you -- and that means it needs to be a choice that you can live with not only at 29, but also later in your life. No matter what you decide right now -- whether to have the baby, have an abortion, or go the adoption route (I know what you said, but I do want to write more about that in a sec) -- it's going to be hard. So faced with three difficult options, you want to make the best one -- for you.
Does the father factor into this picture? Are you married or in a committed relationship with him, and does he know about your pregnancy? Would he or does he want children? Do you think he would be a good father?
If you have an abortion, will you be okay with it later? Some women are, others aren't. At this point, you have already figured out about when the baby would come. If you have an abortion, there will be times when you wonder who that baby would have been, you might figure out how old it would be. You may think it was the best decision, or you might later change your mind. These are the things to think about now. It doesn't matter what your grandmother or the rest of your family thinks. It only matters what you think, and the father, if he is in this picture.
If you have the baby, your life will change. Absolutely. But as Rosa and Alison said, it can also change in the ways YOU want it to. You do not have to define yourself as a housebound slave. You can work. You can find good child care. You will still be interested in the things you're interested in now. In many ways, you can redefine motherhood the way you would like to see it. At first, yes, it's all about caretaking. But babies are mobile. You can be active, educated, and on a path that you want to be on.
If you are hesitant about abortion and feel that you would regret parenthood, I am wondering why you are set against adoption? There are many people -- single, married, straight, gay, younger, older, working or stay-at-home -- who would give energy and love to a child. You would choose. I know you wrote that you are "all or nothing." But sometimes the world just isn't that black and white. You have to be willing to consider shades of gray.
Again, the MOST important thing here is that YOU get to do the work of this decision. You need to fully think about each option and what it would mean for you, and then decide, for you.
Not for family, you know? Not because of what other people say or think.
Please don't be disgusted with yourself. That doesn't help you, it only hurts you. You didn't know you would feel this way. (That also means that you may change again, too. It happens.) Stop beating up on yourself, OK? You have a little time to sit with this decision.
Please write back again if you would like to. I know this is really hard.