I feel like I have produced nothing worthwhile for my PhD in the last two months. I haven't submitted anything to my supervisors in that time. I've met with one of them once to discuss how worried I am. The worry doesn't seem to go away. I cry when I wake up with the thought of how lost I am. Bizarrely I love my subject and I love the idea of researching it - I just don't seem to be able to do it.
I keep taking time off so that I can calm myself down, but I can't do that forever!
I feel sad and lost and I don't know what to do. Have I left it too long to fix this? :-(

Not in the slightest. This happens to everyone. I suggest you read round a few papers, try to copy a few experiments (or do a review paper of your own if you're not scientific) - you may find this stimulates the brain cells with a quality: "what if I do this...?"
Best of luck.(up)

What stage are you at? Are you still researching, or have you started writing things? In either case I'd recommend drawing up a list of what you should be getting on with, then breaking it down into smaller parts. Pick the most appealing item on the list to start with (alternatively read that as the least unappealing!), and tackle that. Then once you've done that move on to the next item and so on. I also find that brainstorming in general helps, to make track of where I am now, and where I might go next. Have you agreed deadlines/targets with your supervisors? Did your supervisor give any advice on how to overcome your worry? They're there to guide you through this process, so make sure they help. But it's definitely not too late. I've had much longer periods of down-time (admittedly I'm part-time so schedules are more fluid) and have managed to pick myself up again. Just in the process of doing it now actually, though a looming deadline helps. Good luck!