How to stop bombarding him with texts?

I get really anxious when my crush does not answer and start to bombard him with long emotional texts. I also start to cry, one day I did that in front of my little sister who got scared and thought I was dying.
I know it is wrong and drives him away but I could not keep myself away from the phone, ask why he doesn't answer and just write huge monologues. It has gone too far but I don't know how to stop. He thinks I'm too clingy and that is stopping us from moving on. I really want to change that and not bombard him all the time but he not answering makes me terribly anxious and act unrationally, even if he hasn't seen my message but I can see that he is online (we communicate mostly through WhatsApp). I would really appreciate your tips what to do. As I think about it, I get anxious again thinking that maybe I've ruined it all already by acting insane but I really like him and want that inner peace so I could be a better friend and girlfriend.
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How to stop bombarding him with texts?
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