Oh my, I totally get where you are coming from. You have all the time with your baby for 6 months, and suddenly, you can't spend that precious time with baby anymore! I had a similar situation at 9 months. I really, really, really wanted to quit. My husband convinced me not to, mainly with the argument that he didn't want to be the sole earner, that was too much pressure. I figured out a way to do my work (school actually) in less hours, and had a sitter from 9-3 4 days a week, (and worked Saturdays while hubby watched baby). This turned out to be okay for me. I felt I still had my special day with him during the week, he was with his dad on Saturdays, and I had shorter days when I did work. I was able to adjust.
In your case, as a teacher, I know you will have no flexibility with your schedule. You would not be the first person to quit your job and look into other options! How much do you need your specific salary? Are there ways you could cut in the household budget? Could you look for something else part-time, such as tutoring? Or are you crafty? Could you make and sell things on your own time?
I guess the bottom line is, yes, it's hard. You will eventually adjust if you have no other options. But, if you have other options, explore them! If it is torture, listen to that feeling, and figure out some other way to make it work!
I will also add that my DS1 is now almost 5. He is not in school yet, but we definitely need the time away from each other when he is in preschool! LOL! Point being that somewhere around 3, you will probably be ready to have some mommy time away, even though right now you want to spend every waking moment with LO!