Hi VanillaBean!
I think you are asking really good questions. I also think that you may get some very different answers from some of the members according to their individual experiences and also the fact that over the years the face of psychology/psychiatry has changed and grown.
I don't think you are at all weird by not telling your T certain things throughout the years because your head was filled with obsessive thoughts. Many many people think that their thoughts and/or traits are normal. They are normal to us and why in the world should we think that they are anything but normal until someone speaks up about them to us? (providing they figure things out without us discussing)
It is also not unusual for people to be afraid to tell their T's everything they are thinking about for many different fears they may have. Trust is a big issue for a lot of folks. There is also the thought that our T's would think badly of us if we told them exactly what was on our minds. It's hard to remember that for the most part, our T's are good people and not their to judge us, but to help us work through our problems.
I hope that you have finally received a good dx and are getting the proper therapy/meds etc.
Take good care!

sabby