There are different kinds of abuse. Although I was molested a couple of times as a child, and also beaten up by bullies, those weren't the things that had the most significant impact on my development. I feel that emotional neglect has a lot to do with it. We have to keep in mind that different people have different needs, potentials, vulnerabilities, etc. That said, here is one possible scenario.

I see BPD as an adult attachment disorder. Babies have to attach in order to survive. They can form secure or insecure attachments. In order to form secure attachments, three things have to happen. The baby has to communicate that there is a need. A caregiver must understand the need and respond appropriately. The baby must be able to be soothed. A number of things can interrupt that process. Maybe the baby isn't able to tell when she is uncomfortable or hungry, or isn't able to cry. The parent might continually misunderstand, and insist on trying to feed the baby, when the baby really is lonely, not hungry. Maybe the baby has colic and no matter what the parent does, he doesn't feel better. There are no perfect caregivers, and everybody has unmet needs sometimes, but if the baby learns that her caregivers are unreliable more often than not, that child will likely form an insecure attachment. As we grow, emotional invalidation also contributes to insecure attachments. When you say that you hurt or you're sad or angry, and someone tells you that you should be just fine, and there is nothing to be upset about, or they tell you that you shouldn't be happy about something that makes you smile, etc., you learn not to trust your own feelings and perceptions either. We grow up with a lot of experiences like that, and we feel alone and we can't regulate our emotions (or understand them even), and it's hard to trust anyone, and we are afraid that if someone gets too close they are going to take over, and we resort to acting out behaviors to try to prove to ourselves and others that we hurt and there is a problem but nobody seems to be able to understand. Any kind of abuse can contribute to the pattern of development. Sometimes we have a hard time recognizing what we experienced as abusive, especially since we didn't know any different so it's normalized for us.

It doesn't matter so much what the label is. There is a reason that you are the way you are. We don't develop mental illnesses just for no reason. Finding what the reason is for you might take some time and patience, but that's okay. And even if you don't know what it is, what you are feeling is real. It is how you feel. And what you do has a reason behind it also. We don't do things for no reason at all. If we are not happy with our choices, we can learn to make better ones.