Hello Pixie,
Heed the words of those written above well. I feel like you do, I am guilted like you are. I remained even though unhappy. I have been this way for the last 15 years of my current 35 year marriage. I have had to try very hard to gather the strength and courage to even consider leaving, as we both are in our 60’s. Dont let time slip away, you dont know how happy you might be, until you try. I regret the years of unhappiness, and wonder how I stayed in this melancholy marriage. It became habit and I did not want to feel guilty, so concerned what others would say or judge me. Just listen to your heart, and visualize a life as it is now, and what it would look like 20 years from now if you made no changes. If it doesnt feel good, you have your answer. “Playing the movie reel of the future” either staying or going, will give you insight as to what you want to do next.