I am so sorry to hear that you are going through such a tough period. I know what it is like to be in a marraige where there is no love. You feel all alone in your own home. It is an empty, sad and lonely feeling.
These circumstances can create the foundation for depression, which only makes you feel worse. The depression distorts your thinking, your perception... it distorts your whole world. When you have thoughts about suicide it is the depression taking over your mind. I have been there. Bad marriage. Divorce. Loneliness. Isolation. Depression. Thoughts of Suicide. Actually planning and ALMOST going through with suicide.
The depression distorts how you think about your life. The glass is ALWAYS half empty. You can not experience any joy.
I discovered when I admitted myself to the hospital after almost following through with my suicide plan that there were many people worse off than I. People with chronic mental illness that had no support, no one to care.
The only way that you can look at life with a "gladd is half full" mentality is to first get your depression under control. Get to your doctor, get a referral to a psychiatrist or mental health clinic in your area. Get the depression under control first. You will not have the energy to tackle your marriage issues until you have the depression under control.
Once you are feeling better then you can approach your husband and begin addressing the issues in your marriage. Both of you owe it to your children to try and salvage teh marriage. But, you both have to want to try. Going through the motions only prolongs the pain and suffering. Both of you need to be committed to giving it your best shot. With a total of 5 lives on the line I think that it is worth a concerted effort.
I wish you the very best of luck in feeling better and moving forward. You can do it. Try and focus on the blessings in your life and get the help you need.