If a guy thinks I'm too clingy, why does he come back to me every few months?

I feel like I always mess things up with him, each time I'm the same way. But then why does he always come back after 2-3 or 5-6 months? He never dates anyone else in between the times he's with me.
If a guy thinks I'm too clingy, why does he come back to me every few months?
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