Hi there "dazed and confused",

This sounds like a big fat case of 2nd year blues. I was in the same boat 8 months ago. I was literally walking into my supervisor's office to let him know that I was quitting and my phone rang. Something very small, but it stopped me. I went and spoke to a postdoc - had a very long cry and was told what I am telling you now... you're half way through it. Time is ticking indeed, but if you quit now the past year and a half would be a waste of the time ticking by.
I dusted myself off, took a big deep breath and made myself get into the lab the next day. It isn't easy, in fact its so hard - the isolation, lack of confidence and being totally overwhelmed - but when you get through this "dip" you will feel so much better.
If the support isn't there, get it. Take control and make some noise, let them know you need it.
I have realised now that PhDs aren't just here to test your intelligence or academic ability, its also here to test your character (half destroying it indeed, but... )