I want to send threatening text messages to my boyfriend.

Hello, although you sent a message to the other party, it is not a threat, because according to our laws, general intimidation is not illegal. And if the other party hurts you, you must bear legal responsibility. So you don't have to worry about texting. But to solve this matter, there must be evidence to prove the other party's behavior of hitting you. I suggest you report it to the police. Besides, you are doing an injury appraisal to determine the other party's liability for compensation. That's basically what I did. I hope my answer is helpful to you.