Yup, that's probably overtraining. Very typical. It's the intensity, mostly. Back that off. You'll lose a lot more fitness to overtraining than to backing it off. When I get like that, I'll also usually notice that I'm using smaller gears climbing, my heart rate doesn't come up as much when I climb, and that my morning resting heart rate is up about 6 beats.

I was once overtrained a whole summer. Did a lot of rides, too, but was slow.

You don't mention using a heart rate monitor. I find that a HRM is the best tool you've got for preventing this. I finally went to a recording HRM that I can download into my computer, so that I can keep track of and therefore limit my intensity for each week. It tracks my time-in-zone. I also take my morning resting heart rate every morning, and put that into my training software, so I track that, too. That's a big help.

If you're using a HRM, you can back it off until your HR once again pops right up to over lactate threshold on a steep hill. Then you're good to go again.

But good for you for wanting. That's a good thing. When you lose the wanting, too, that's bad.

I'm not even breathing hard.