I’m thinking you two had different definitions of “taking a break”

He definitely was cheating. You are better off.

So is he your ex of 5 years or your ex of 5 months? The fact that you called him your ex kinda implies that the relationship was over, but then you said you were just "on a break", but whats a break? Not seeing each other while still being exclusive with each orther or a time to explore other options? 5 months seems like a long time to be on a break...This seems like a complicated situation that you probably don't want to be a part of. It's probably best to move on.

“Taking a break” is the diplomatic way of saying “breaking up.”

No one owes you anything during a break, should have made an effort to get back together

Okay so I read it like this - OP and their ex were together for 5 years. They then "took a break" which has lasted 5 months. Ex got engaged during that break to someone. Ex probably wasn't interested in marrying OP, and was staying with them for lack of better options. That's why it was a "Break". Because if they couldn't find anyone better, they probably would have went back to OP.

Come on. A 5 months break is called "moving on". How could you expect him to be exclusive to you after almost half a year of not being together anymore?

come on, man! You should know "a break" is never "just a break".