I'm going to give this a shot.
Dear Ex,
I have asked you to stop contacting me as we are unable to find a balance between our lives that allows us to be friends. It's no one fault, just choices and circumstances.
But for the love of GOD stop contacting me!!! I asked you nicely a few times, and now I am getting angry and can't move forward. I have not replied to the last seven messages you have sent in the last three days. I am sure you are desperate to talk to me since your boyfriend is completely emotionally unavailable for you, and only wants to see you on weekends (for sex, I'm sure).
Begging me to talk to you and calling me Baby is pathetic and manipulative and needs to STOP NOW.
You want to know how you can "fix it" like you said you wished you could do? Dump your boyfriend. Be ALONE for six months. Grow up, find some independence, find some self confidence that you don't need to be with someone so you can offer more than instrumental motivations in a relationship. Then, and only then, contact me. We will talk about how difficult it was, but how you feel much stronger and are happy with yourself.
Otherwise, go complain to your boyfriend about how much you miss me, and see how he feels about it.
Heated,
R