There's some nasty stuff going around. It may just be your body is still working to recover from this.

H1N1 knocked me on my ass in 2010. It was three months before I didn't feel weak all the time, and fully nine months before I felt myself again. This past February, I was out of work for a week with something similar. Twelve weeks later, I'm still inconsistent--one good day followed by several not so good ones--and I fatigue easily. My numbers are down across the board, except for heart rate which is up by 5-7 BPM. I'm embarrassed to report that on Saturday's club ride I walked a short 12% grade--only the third hill I've ever walked. (There's a 10% grade on my commute too.)

If you had something similar, it may just be your body is responding in a similar way as mine.

Ease back a bit, pay attention to nutrition and rest, and form will return when your body can support it.