He's already shown you he's not interested. You need to back off and leave him alone. If a man is interested in you, he'll directly tell you he is. There won't be any signals for you to have to read into or interpret or analyze. He'll just say it plainly enough for you to understand. But your ex-bf hasn't done that. He's moved on. You need to move on.

Texting him your new cellphone number was a huge mistake for yourself, b/c you did that to set up expectations for a future reconciliation with your ex-bf which is not going to happen. He only responded to your text "thank you" out of politeness. You should delete his cellphone number from your cellphone. Otherwise, you will be tempted to incessantly text him to try to get him to respond to you.

Chasing an ex-bf is never good. It shows him that you lack self-esteem and makes you come across as desperately reaching for something he isn't willing to reciprocate anymore.