1. Feed times should be timed and the baby should feed every few hours.
This isn't true. Feed your baby when your baby is hungry. There will be times when they are going through a growth spurt, and they want to eat all the time. Then they'll go through a time when they are not growing, and not as interested in eating. I found that when my babies had a cold they ate less, when they were getting better they ate a lot!
2. You can't have enough milk to feed that baby so often.
Most women's bodies accommodate to how much the baby needs. Some people have problems producing enough, and some people have problems producing too much. Once you've nursed for awhile successfully, your body will accommodate to what your baby needs.
3. You have mastitis, so you must stop nursing!
You should keep nursing, and talk to your doctor about what to take to help you get over the mastitis. Otherwise your milk supply will go down.
4. Your milk is too strong or too weak.
Breast milk is just right for your baby. It does change as time goes on. In the beginning it is more yellow from the colostrum you have in your milk. Colostrum helps fight off infection. There are times when your milk is more fatty, and times when it is more watery.
5. Too much milk can make your baby overweight.
Not true. Babies are just sometimes fat. I've seen a lot of toddlers that are skinny, when they were fat babies. Breast milk is balanced right for your baby. Some babies do better with shorter feedings. That is if they spit up a lot. There is nothing to worry about if they spit up as long as it doesn't smell, or a funky color.
6. It is impossible to get pregnant while breastfeeding.
This is not true. It's harder to get pregnant, but it's not impossible. Talk to your doctor about birth control pills to go on. There are different pills they will prescribe you while you are nursing.
7. You should only nurse your baby for the first few months.
This is the recommended time. I see anything additional as a perk. Really it is between you and your baby. If you feel done, then it's time to start weaning. If your baby is done, they will start weaning themselves.