Relationships evolve. You are equal partners in your relationship. It suited you both, not just him, for you to stay at home when your children were tiny. It wasn't some big favour either he did you or you did him. It was what you both decided was best for your family unit at that time.
The thing that gets me is that he seems to view you as some pawn that he can move about the board depending on what suits him best. If it suits him that you should be a SAHM and housewife, fine. If it suits him to put you to work in a minimum wage job, also fine according to some posters above. But you're not some kind of donkey that he owns. You're a person in your own right and his life partner.
This shouldn't be how relationships work. Yes, he isn't solely responsible for supporting you and the whole household indefinitely, but he needs to acknowledge you the person, with dreams and aspirations but also thoughts and uncertainties of your own. He shouldn't be dictating to you what you need to do going forward, but you should both be supporting each other to achieve your life and work aspirations. You've had a number of years in the thick of family life - the sleepless nights, the exhaustion, the focus on the day-to-day, the boredom that comes with caring for very young children.
Having children changes you, especially if you're the person carrying 95% of the physical and mental load. It is very easy to lose yourself and some of your confidence during this time, especially if you take longer to get back to work, where you have a separate and distinct identity. And when finally your children are sleeping through and don't require your constant attention, and are becoming a bit more self-sufficient, suddenly you start finding yourself bit by bit again. I remember having a moment when I thought "oh there you are!" and I finally had the energy and mental headspace to connect with the person I was pre-DC again.
Unless you as a family are in a financially difficult place, I don't think he has any business demanding that you go out and get any job that you can the minute your youngest is in school. You did what you did for the benefit of the family, including him, and he at least owes you the courtesy of giving you time, and investing sufficient resources in you, to help you to work towards a job that will enable you both to contribute towards the family financially and have some degree of work satisfaction and prospect of progression. Anything else is just disrespectful of your marriage - it is a joint project for your mutual benefit and the benefit of your children, not a sole project purely for his benefit.