Thanks for your e-mail and the question you raised. I would encourage you to talk with the elders at your church, as their response may help to determine or to confirm the decision you reach. I will also make a few comments on baptism which I hope will be of some help.
I think we would all agree that the baptism of the New Testament is "believer's baptism." From the examples we find in the New Testament (e.g. Acts 8:26-40; 16:27-34) we should also conclude that ideally baptism should happen as soon after conversion as possible.
Given these general guidelines, I think part of your agony is that your baptisms years ago were less than ideal, primarily because you are somewhat uncertain as to whether or not you were really saved.
In Acts 19:1-7 we have an example of a re-baptism. These folks that Paul came upon at Ephesus were familiar with John's preaching - that the Messiah was coming. They received John's baptism, which was a baptism of repentance in preparation for the coming of Christ. But since these folks had not been baptized as believers, they were rebaptized when the Gospel was proclaimed to them and they received it. Thus, here we have a clear case where rebaptism was required.
I think that if you are really not certain that you were baptized as believers rebaptism is something you should consider. I would say that for those who are certain they were baptized as unbelievers they should (indeed they must) be rebaptized, as believers.
Having said this, I should go on to point out another factor. If new believers are baptized almost immediately after their baptism, they are far from being a mature believer at this moment in time. They must know the essentials of the Gospel, but they would surely not grasp those things that accompany maturity (see Hebrews 6:1-3). Baptism, then, is a commencement exercise, a symbolic initial act of obedience that will be understood more fully only as one matures. That is why (as I understand it at least) Paul argues on the basis of a believer's baptism in Romans 6:1ff. Paul argues there that baptism symbolizes one's death to sin, in Christ, and one's resurrection to newness of life, in Christ. If one has died to sin and is alive to righteousness in Christ, how can he continue to live in sin after his salvation (and baptism, which symbolizes their death and resurrection)? One should not expect to fully grasp all the truth at the time of one's salvation.
All of this is to say that I think each of you needs to determine whether it is your salvation that is in question at the time of your baptism, or whether it is your maturity. If you have doubts about your salvation, you may very well decide that you should be rebaptized. If you are only wishing that you were more mature at the time of your baptism, I would suggest that all you needed to know was the basic Gospel, and to have trusted in Christ alone for your salvation. Though I was baptized as a young believer, I surely did not grasp all that this symbolic act entailed.
It seems to me that in the final analysis you are really struggling with what falls into the category of a "personal conviction." Some in your place would probably not be rebaptized; others would. Paul's guidance is that you should be "fully persuaded in your own mind" (Romans 14:5). Paul concludes this chapter by informing us that "whatever is not of faith is sin" (Romans 14:23). My advice, then, would be to deal with this question as a matter of personal conviction. When you have determined your personal conviction on this, so that your conscience is clear before God, I would do that - whether this is to be rebaptized, or not to.
I hope this will help in some way to clarify this matter for you. Again, I would encourage you to raise this question with your elders.