I don't think you can sue your ex-boyfriend for legal malpractice, no. Initially, there was no attorney-client relationship between you two: he was your boyfriend. Indeed, you had a divorce attorney -- which also argues in favor of your ex-boyfriend not representing you.
Best of luck to you.
Cary B. Hall, Esquire
Law Offices of Cary B. Hall, L.L.C.
121 East Chestnut Street, Suite 205
Souderton, PA 18964
T: (267) 663-9995
F: (215) 525-4364
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