Tigerlily, I'm very sorry to come here and read that you had a very dark day. I do hope that things are a bit better for you now. I know that things are very difficult in your home right now, but please do not ever consider taking your own life. You do not want to leave your son this way and have him wonder in years to come if he may have been the reason why you considered taking your own life. Your son needs you and your family needs you. If you get those feelings again, please call your local crisis hotline and talk to someone.
About the cat, does she have a large litter box? Maybe the cat doesn't like the type of litter you are using. There has to be some reason why she's not doing her business in her box. It could be she senses the stress in your home as animals are sensitive to such things. Go on line and google "My Cat From H@ll". They had a show just last night about the cat not using the litter box. You may be able to get some ideas from that show. Please don't put the kitty out on the street and leave her homeless. If you have to give her up, call the local Animal Rescue League and have them pick her up and hopefully they will find her a new home.
I do hope today is a better day for you. I am keeping you and your family in my thoughts and prayers.
BTW, it's time for you to think about a new thread.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.