I know I am not the healthiest eater, so how do I make sure my child receives all the nutrients he needs?

If you are breast- -feeding, your breast will take away from you the nutrients you need and give them to the baby. Start eating healthy before lactation pushes you over into real malnutrition.
Offer healthy foods. Try to keep healthy foods around and offer them to your baby. Remember it may take eight attempts before a baby gets used to a new food. The most effective way of ensuring certain behavior is to be a role model. It would be a good idea for you to try eating more healthy foods.