No one is obligated to tell their current SO about past relationships. They can choose to if they want, but it can often cause problems because the new person may feel like they have to compete.

Idk, we've been together for 30 years and the only past relationship of his I know about is his ex wife. I could care less about any other women in his past. He married me, not any of them. The one he did marry didn't last a year. Apparently she had difficulty keeping her knees together. 😱

If you had told him in the beginning about talking to your ex, the reaction would have been the same. Get out while you still can.