There could be several reasons why your ex told you that he's happy without you:
Moving on: Your ex might genuinely be in a better place emotionally and have moved on from the relationship. After a breakup, people often go through a healing process, and it's possible that he has reached a point of acceptance and contentment in his life.
Self-assurance: Sometimes, people say they are happy without their ex-partner as a way to reassure themselves and others that they are doing fine after the breakup. It could be a way for him to project a positive image and show that he's capable of being happy on his own.
Emotional defense mechanism: Expressing happiness without you could be a defense mechanism to protect himself from feeling vulnerable or showing signs of lingering sadness over the breakup.
Seeking closure: By asserting that he's happy without you, he may be trying to establish closure for himself and finalize the end of the relationship.
Avoiding confrontation: Telling you that he's happy without you could be a way to avoid further discussions or potential conflicts about the breakup.
Trying to make you jealous: In some cases, an ex might say this to make you feel jealous or regretful about the breakup.
It's important to remember that people cope with breakups in different ways, and what your ex says may not always reflect his true feelings. It's essential to focus on your own well-being and healing process rather than dwelling on his words.
If you are finding it difficult to move on or the statement has deeply affected you, it might be helpful to talk to someone you trust, such as a friend, family member, or a therapist. Give yourself time and space to heal, and remember that your happiness and self-worth are not dependent on your ex's words or actions. Focus on self-improvement, self-care, and surrounding yourself with supportive people.