Perhaps there is a complicated problem if this issue has been an issue for years?! Since you are a first time poster... and nervous... I am not sure we got all of the details. Giving definitive advice isn't something that I believe should be done on such a low amount of information. For one, when did these thoughts first occur? Was it because of a specific event or time period? Depression can be nutrient based, genetically based, a result of certain medications, and/or historically based. If the depression/anxiety/guilt/thoughts of Depression are affecting your everyday life, make sure professional help is sought. Use your intuition to decide what level of help you need.
The historically based problems are difficult, but not impossible. If somebody harmed you, it may be difficult to overcome or at least get a handle on. There are lots of resources here on Curezone (as has been mentioned in other responses. And, in addition to the nutrient and toxicity issues, there are other things that you could do. Depending upon what you are open to, you can look into the Awareness and Consciousness Forum , the Spirituality Forum , and the Christianity Forum . Harboring anger can cause many problems. Remember, of course, that guilt is anger at yourself or your actions and can cause the same problems as anger toward others. Learning to acknowlege feelings, and then coming to peace with them can be very cleansing.
In terms of feeling like you are ruining your husband and children's lives, why is that? Are you feeling unfulfilled in some way? What can you do that would make you feel more beneficial or at least fulfilled? Are you an artist who has stopped producing? Do you have a phD that is sitting in the closet gathering dust?
Lastly, a little inspiration:
"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. " ~Bertrand Russell