The kind of jealousy that your boyfriend is displaying needs to be dealt with sooner rather than later. You’re right that it’s out of control, inappropriate, and for you to have left.
Men who are trying to control their women at that level are operating out of a profound level of insecurity. This insecurity and jealousy and Are being dealt with by trying to control you. You do not want to be with someone like this.
Don’t make the mistake many women in your position make by going back thinking it will get better. It doesn’t — not without a lot of emotional work and therapy on the man’s part. For future relationships or if you do decide to go back to this one, I would be very clear about the fact that if you wanted to cheat on him nothing he does is going to stop that: Trusting each other is the only thing that will work.