It is difficult to read the responses to your post and remain unbiased in my response. I hope I can be of help.
I was raised a PK (preacher's kid) and lived always, it seemed in my Dad's shadow and the shadow of his faith. What I did not know of at the time was that Dad had his struggles and doubts as well that he did not make me privy to. Part of this "arms-length" attidude I believe now was his fear that he might negatively influence me if I were to discover that he wasn't quite the hero that I looked up to. Our family life was lived in a "fish bowl", at least what Mom and Dad chose to reveal to the folks at church where he ministered.
I had some real fears of my own at the time and serious doubts of my salvation that I think embarrased him. He and I both wrestled with the contradiction that we saw between what our hearts told us and what we assumed the "ideal Christian" should be.
I'll summarize to say that I think my doubts were (and sometimes still are) due to the error of thinking that I can please God on the basis of my own merits. I think that a large reason for most doubts as you describe stem from our own stumbling into legalism and works to attempt to justify our actions or feelings.
The obvious answer from scripture is to move our focus off of ourselves and onto the sufficient and glorious grace of our Lord and Savior Jesus Christ.
One more quick note: In my adult life, my wife and I lost our first child, Michael who was born premature and lived only months due to complications and prematurely formed organs that were unable to function properly. I was driven into a deep depression and despair that seemed to have no way out. My wife feared that I would take my own life and I began to be assailed by doubts of my own salvation.
I came through all of this only by God's wondrous grace. This experience provided me another clue to these doubts that in this instance originated in the loss of our child and that I had somehow participated in his death as a result of my disobedience, unfaithfulness to God, etc. I wanted to blame myself for Michael's death and in so doing, I labored under false guilt that was manifested in my doubting of my relationship with the Father throught Jesus Christ.
I think there is a difference between genuine and false doubts as well as worldly and Godly repentence and the distinguishing of these is in their outcome, or fruit.
