What would you do if you were disatisfied with your marriage?

What if after five years of marriage you notice your marriage is not in any way what you envisioned at the time of marriage? If your life was constantly improving, work, finances, health, but yet you realize that your life with your spouse is not fun at all anymore, is literally non existent, you could not express thoughts, feelings, emotions, wishes, dreams...etc. without the fear of being critized or ridicule (by you spouse)...sooner or later. Adultery was not a factor. You realized that contrary to what you believed when you got married, the two of you don't really have anything in common. One day you just got tired of waiting for a change gave up hope, and decided to do something to get your life back to the way it was but you realize you have indeed changed so much that you don't really remember what it was like. If there was no children this would be a no-brainer...but. What would you do if at the age of 30 you realized you were married to a frigid woman????