An Epiphany

Last night someone asked me why I don't believe in soul mates. The answer is simple: If there is such a thing as one perfect person for each of us, or a "twin soul," then I've already found mine. What's the point of continuing the search for something you already have? Except I don't HAVE it. I did have it, once upon a time, but he's getting married in November. If I believe in soul mates - in the truest sense - then I will spend the rest of my life alone, always pining for what was once within my grasp. I am not that nihilistic.
I once believed that maybe there exists a variation of soul mates, which would allow that there are multiple people with whom we could easily share a fate. I came to this conclusion as a result of having loved very deeply a second time. But believing in multiple soul mates is also problematic. How do we decide what the appropriate number is? Could anyone be a soul mate if you happen to meet them at the right time and in the right place? Or are there certain mystical connections necessary to form that kind of attachment? How does one "prove" or "disprove" whether their partner is a soul mate?
I don't know what to believe anymore. I opened my heart twice; each time I was hurt so thoroughly that I've not yet begun recovering from either. The most recent was a year ago, and that wound still aches like a stubborn brain cancer. At least I have some temporal and geographical distance from my first love. I can look a that more objectively sometimes. But this past one throbs to my core.
I feel like a 28-year-old divorcee. I can't imagine ever loving someone that way again. Not because I don't want to, but I don't know if I'll be capable. I can't fathom having to face that pain all over again, feeding off the unhealed wounds of the past, torturing my dreams and waking life. Some people say they feel a void when they face loss. Where my void should be, there is nothing but pain. Sometimes I feel like it's my fault.
Not because of anything I did or didn't do. There's no sense in mourning events of the past. I was brought up believing that love is forever, unconditional, enduring and fulfilling. Sean Connery once said "I can't love people in slices." That's exactly how I feel. When it comes to people I let into my heart, it's all or nothing. And sadly it's not interchangeable. I can't force it to become nothing once it has been everything. And so I love people with very fibre of my being. But that isn't enough.
My first love still loves me, but he chose a different path. My second love hurt me so deeply that I cannot be with him in the foreseeable future. What is it about me that does not inspire those I love to reciprocate in the way that I deserve? Why does it seem like too much to ask for others to love me to the same depth that I love them? In this way, my pain is my own fault. Because I loved people who either could not or would not live up to my expectations (I tend to think it's the latter; if I'm capable of this kind of love, surely I must not be alone in that capacity. This means that they refuse to reciprocate on the same level).
I don't really know how to move forward. All I understand right now is to be stuck in the past. Maybe it's because the future is frightening to me in almost every way. I may eventually meet someone and think about loving again. Will I be able to move beyond the past? If I can, will he disappoint me as the others did?