I don't believe in soulmates. At least in the sense that there is just one for you. I guess that always bothered my recent ex too. But I just have to be realistic about it. There is no way that there is just one other person out there for you. There are many, many people out there who would be compatible with you and add to your life. But you still of course have to sift through lots of potential candidates until you find those compatible with you.
No, and you don't.
Read Journey of Souls by Michael Newton if you're curious. There's always a certain soul that's close to us in most incarnations (depending on the purpose of that life) that is essentially your "soul mate". You don't always marry them or even meet them in every life, but you're close in most of them.