Wow. I am also a mother of three and I work full time. I know how you feel about sitting and wanting to cry at the end of the day (which is usually late at night.) you look for someone to talk to, and no one seems to be there.
You need to get health insurance. Just this one thing, I feel, would do wonders for you in helping you not to worry. When my oldest 2 children were young, I was on state medicaid. See if your town has this available. It is usually through the department of health or equivalent. You may also find information about this at your childs' school (if they are young). Setting your concerns for your health and your childrens health will be a tremendous burden off of you, and hopefully will allow you to tackle other issues afterwards.
My best to you

You're body is most likely exhausted and you have so many people relying on you, that you are fearing the worst: that you may not be there for them when they need you. Here is my advice for the interim, and I am not a doctor or anything, but this worked for me to an extent. I know you've heard this before probably, eat more healthy foods (vegetables, fruits, lean meat, etc.) slow down with the caffiene at night, if you drink it. And try taking a multivitamin every day.

Hi there. Im a mother of 3 and work full time myself so I can totally relate to you!! My suggestion to you is this...See if your state offers some kind of free medical. (in california its medi-cal as an example) many years ago I was on it because I wasnt working due to health problems and had no coverage and it worked for me. My other suggestion if you can't afford meds, etc is to see if you can afford valerian root. Its natural and will help relax you. Now adays, they say that taking kava kava (which has nearly the same effect) is not good for you so I would stay away from that. As the other nice person said (sorry cant remember your name:( limit soda's and coffee's later at night so it doesnt keep you up. Try a hot bath before bed also, that is very relaxing. And if your kids are old enough, see if they will rub your feet/back to relax you. Good luck hon and you are not alone! Take care.

Jeannine