There are no magic formulas to win someone back, though sometimes we do things inadvertently, not realizing they are fueling conflict or making things worse.
In BPD relationships, it's easy to fall into the trap of appeasing, fixing, rescuing -- doing anything to make them feel better or get them to dial down the conflict. As a result, we become needy (not attractive), and feel bad all the time (not attractive).
How different are you from being the person you were when you two met? People with BPD don't have boundaries, so you have to be the one who provides them. It seems like he wants you to be strong, and in response, you are clinging, saying anything you can to win him back.
What would happen if you presented yourself as having confidence, being yourself awesome self

LnL