That is very disrespectful and tells you exactly how he really feels. If someone could say that to you then they need to learn how to filter what comes out of there mouth. Not cool and I couldn't have someone say that to me and still believe they loved me and my child.
Leave him. Although he has some serious issues within, he shouldn't have said that to you. He's your husband and you're his wife but unfortunately, there's no room of respect or appreciation for you in his life anymore. A simple word is like an oral sword, so get him out of your life. Don't depend on him anymore, for if he doesn't alter himself, i would wager you that things would get a worse. Comfort yourself and your son for now, or talk to the rest of the family or friends that would understand the situation. Or, defend yourself. You have your right too in this so don't let him pressurise you, and the son too. Be strong, be strong. DON'T SURRENDER TO THE THINGS HE SAID.
Time to start over, my wife of 24 yrs has never been a burden! or my sons!! How could he say such a thing, move on with your life and show the loser what a real burden is like... Life without both of you!
Then you've been able to hear how he truly feels. Do you want to continue living with him, knowing this? Put your son first. Is this how you want him to feel? As a burden, and ashamed? Move on. You're working now, so work to improve your life- by yourself. You don't need anyone to 'save' you. Self-respect is a wonderful feeling.