First, when you find out you're pregnant, sometimes even before you know, your boobs get REALLY sensitive and sore. I remember having to stand backward in the shower because even the water hitting them would hurt! They continue to hurt as they get bigger and bigger.
Then, you grow out of all of your bras. I went up one full cup size when I was pregnant. At this point you might as well buy some nursing bras because you're going to live in them for the next two years. But here's the thing, you can't buy to fit you NOW because you'll go up an entire cup size once you have the baby.
Once you have the baby, not only does your milk come in, causing them to be engorged and hurt like hell, but you also have to adjust to a person hanging off of your boobs for the majority of the day. Yes, you are now an all you can eat buffet for a little person that eats every hour. And boy does it get tiring. Not to mention painful!
Think of someone yanking on your nipples for 30 mins, every hour or two. Then, rubbing sand paper on them right after. Your nipples get so chapped and cracked, it's common for them to bleed. The only thing that can possibly help is rubbing this sticky lanolin paste on them after every feeding.
Then there's the issue of booby leakage. Yes, it's possible your boobs will start spraying milk at random times throughout the day. I've been told stories of my sister-in-law chasing people around, spraying breastmilk at them. And yes, you can get distance with those suckers! Be careful to pad your bra with nursing pads or your bound to wake up in a puddle, or elicit stares from strangers as you walk by.
Perhaps the most daunting though is the fact that your body is now the property of someone else. It was this way throughout the pregnancy, but it's so much easier when you only have one body. Now, you have to take the both of you almost everywhere. I've had to nurse the baby while going to the bathroom, while taking a shower, in my car, and several other places, you wouldn't think of.
Breastfeeding takes up most of your day. You have to plan errands around it, you have to adjust your sleep around it, you have to adjust your wardrobe around it. It's so difficult, yet so rewarding. There is nothing better for your baby than breastmilk.
Eventually though, your body gets used to breastfeeding, your milk supply adjusts to what your baby needs, relieving you of engorgement and possibly leakage, and your boobs return to normal. Well, normal plus a few stretchmarks and a few inches of sag.
"A pair of substantial mammary glands have the advantage over the two hemispheres of the most learned professor's brain in the art of compounding a nutritive fluid for infants."
--Chief Justice Oliver Wendell Holmes