Who decided one person should fill your every need for ever and ever until death do you part?

(Sorry in advance for the length – it’s complicated)
Background: I met my husband 23 years ago. We became friends and got married because we liked each other and both wanted children (not a great reason to get married). We have weathered lots of life’s storms and stuck by each other through them all. I know he loves me. I also know I have never loved him the way I should have to have gotten married. I just assumed from our friendship everything else would magically appear over the course of our years together. There was never any passion or “I would walk through fire for him” kind of feeling. We work through challenges (most of them) and have a decent relationship. We have issues – like anyone, but we continue to try and work on them.

About a year ago I became close friends with someone, one of my husband’s friends. Over the course of the last year we have become closer and closer and I would say we are “best” friends. We talk multiple times a day, give each other positive input and support, and we’ve even had our disagreements and issues. It has become a relationship where we love each other. There are times when we are attracted to each other, have discussed it and made definate choices not to act on it. It would be wrong – hurt others in our life and just overall is not right. This is not a case of “the grass being greener somewhere else” – as a matter of fact right now this guy’s life is a train wreck in slow motion. This guy and I share so many interests, hobbies, beliefs, and have so much fun together and even seem to cope with challenges together well. His life is so topsy turvey right now he couldn’t have a healthy romantic relationship if he wanted to.

The Dilemma: The feelings I have for the best friend interfere with my day. This has never happened with anyone else over the course of 23 years. I tend to make him as important as my husband in my choices and time management and spend too much time thinking about him. I might start the day out fine, with everything in it’s proper perspective and place – but at some point during the day, I might start thinking too much about him, feel physically attracted to him,be jealous of him going out with “sex girl” (girl he is seeing to have sex and stay sane), or just plain miss him a bunch and have to make plans to do dinner together or find and excuse why we need to see each other. Husband has on and off gotten very jealous of the relationship and had to be reassured we are just friends and would never do anything to hurt him. My issue that comes up in my mind daily is who ever thought it was a good idea that one person would meet another person’s needs for their entire life and came up with “marriage”? People change and grow. Am I cheating myself out of a richer life and perhaps not living up to my potential as a human being by having myself shackled to another person in “holy matrimony”. Maybe this is just normal for long term relationships that a person would feel this way? Maybe I owe it to the husband and kids to stay put and “stand by my man” because I made that commitment? Is it really healthy to love someone else that you aren’t married to? Why am I driving myself crazy loving someone I can’t be with because niether of us is technically “available”? Why does this have to be a daily mental struggle? How do I fix it?