Its a difficult one to dissect. Especially here, in this forum. Perhaps knowing there is something wrong and you admitting it is a step toward a better life. I'm gonna ramble on about a few things so bear with me.
Humans are basic creatures, we crave attention and to be needed. Like a moth to flame we are the same when it comes to attention. Now we mustn't mistake attention and desire for love. Its something that needs to be evaluated carefully. Also the idea of a "soul mate" doesn't necessarily depend on what you mentioned. Rather its someone that vibrates on your level (this is a very abstract thing to understand) , someone that when together puts you on a different state of mind. From what I understand, you are getting caught up with the idea of something rather than fully understanding your feelings. Ultimately, if you don't entirely understand you, you cannot fully engage with another person. A person has no right getting involved with someone else until they have worked out exactly what they want... You have to be a complete person (this whole better half crap is utter BS, you complete you and no one else!!!!!! )
Relationships then are a craving to obviously to relate to one another and usually when people are unable to relate or understand is where things break down. Right now (in this culture of Tinder attention seekers etc) where its easier to just give up and give in than to sit down and work at the base of the problem is where things start to get tricky. Of course you haven't done that but already the idea of entertaining another person is paramount in a marriage to being unfaithful.
Openness and honesty are key here, talk talk talk and talk it out. Pick up any of the relationship books or self help books or even therapy and you'll see its about understanding and giving attention and meeting their base needs as much as they need to meet yours. At the end of the day, its your choice and there is always choice. Choose the one that perhaps makes you happy (truly and honestly happy!!!!!!!)