How about seeing a doctor? Just to discuss your concerns? You may just be stressed out... you do have 5 kids, a ton of stuff to do at home, the recent loss of loved ones, and chronic back pain..... See a doctor and let them help you!
I am not a doctor.... but it sounds to me like you are under alot of stress... discuss it with your md....
Here's a teenagers POV, if you will even read past this point.. :P I have been treated for depression + anxiety since I was 8, so I have a little experience with that too.
My dad died when I was 8, he was a doctor and it was of a drug overdose (I actually learned this last year..was rough), and we had 5 kids at that time. My mom stayed at home and took care of us, and held the family together when he was in bad times.
My mom is widowed and has 6 kids now, and things have been rough big time BUT she always takes time for herself. That's the most important thing. I don't know what it's like to have 5 kids. But I do know, from my experience, that I love my mom so much and I know she works extremely hard, and I feel relieved when I see her relaxing on the couch watching TV or napping, or going to the gym, talking on the phone with her friends, going out to dinner,etc.--anything for her. Because I need to know she's happy. When she's happy I'm happy. Keep that in mind. You have many children, and maybe you feel obligated to always be sacrificing for them, but that's not the most important thing actually. Don't feel bad for taking time off for yourself. In fact, feel good about it. Do it as much as possible. You deserve it. Really, you do. I'm sure your kids love you so much and would like to see you happy more than anything else. And enlist them to share in the work if they're old enough. I have always liked to know that I am contributing in some way, and it made me feel important as a kid. You shouldn't be the only one who has to carry those burdens. And your kids will thank you when they're older.