Let's just get to the point. Marriage can be crazy hard. From slight inconveniences to heavy devastation, the emotional roller coaster is endless. But there is more to marriage than my own happiness; there is more to marriage than my individual needs being met. Our hedonistic culture seduces us into believing that if things in my marriage are not perfect, not pleasing to me at that moment, then I can just pick someone else. Believe me, I have battled that thought pattern over the years. But the teachings from scripture explain an entire spiritual dimension taking place.
In the very beginning when God designed marriage, he said that man and woman will come together and become one flesh. Do you know what that means? Two people are literally becoming one body. Yes, I know that you can still go get your nails done while your husband plays golf (Praise the Lord!). But there seems to be a whole spiritual aspect that takes place when we say "I do," a converging of bodies into one. That could be part of the reason why divorce hurts so very badly.
Every situation is different. Every marriage has its own set of struggles, some small and some huge. But if you call yourself a child of God, He is faithful to guide and lead. I can tell you honestly that there is hope. It doesn't always have to be the same it has been.
I know this topic gets sticky with "ifs," but God is in the business of bringing dead things to life. Seek His face. Find godly counsel. Hope in Him.