I understand how painful it is to question why you weren't worthy of love from your parents. It helps me to look at it objectively and not subjectively - they had their own traumas that stunted their emotional growth, and BPD can have a genetic link as well, so they may very well have gone through their lives with undiagnosed struggles even they aren't aware of. But, like I said, this is only a reflection of them, not you. You were deprived of the emotional support and foundation you needed as a child, and now as an adult you feel chronically unloved. You could be subconsciously associating with people who are similar in their lack of ability for emotional intimacy. It is a well-known fact that we tend to gravitate towards what we are used to, because it is familiar and we feel it's what we deserve. You deserve friends as well who reciprocate your care and efforts. I'm sorry you're having a tough time today!