Lulu, sorry for highjacking your thread!
CC, I too have confidence issues. For me it's more that I KNOW I can do the research/write the thesis, but it's the other stuff that scares me senseless (presenting at conferences is a HUGE one at the moment!). I had a huge meltdown yesterday in the middle of a supervisory meeting! Was so overwhelmed with it all! It doesn't help that I have a lot going on in my life (outside of PhD) at the moment.
I've decided that self-doubt must just be a part of the PhD thing, but if we get through it, then the light at the end of the tunnel will be worth the struggle