Staying in a bad marriage

I'm curious to know if there anyone here like myself that is staying in a bad marriage/relationship.. I have been with my husband for 12 years. We have three kids, a home and we've built a life together but I am not happy with our marriage. While I was pregnant with our third child last winter-my husband did some things that are unforgivable and I fear it has completely destroyed my relationship with him emotionally. I pretend I'm happy and that I love him for our children and for security.. I have nobody but him and his family. If I leave-I will have nothing and nobody. I'm not even sure I could support my children on my own. I gave up my career 4 years ago because he wanted me to stay home so he could take a job out of state. I stay because I'm afraid of change and afraid to be alone.. plus my kids adore their father and would be heartbroken if we split apart...but I can't imagine living the rest of my life in a loveless unhappy relationship.