I agree with the others, although you should maybe consider if anything else in your life has changed to cause this affect. Perhaps you're stressed about some life worry.
I had a similar experience when I did Hapkido for a while. For the first several months I'd never miss a class, then my attendance began to dip. Eventually it turned out that the problems outside the dojo - namely my life - was full of stress, and I then went to the Doc and was told I was Clinically Depressed!
I'm not saying that's your problem, but perhaps a life worry could be at the route. Taking time out is probably the best thing to do, then see if the need for Aikido returns. Also consider that sometimes you can be training too much anyway, and your body is telling you something. Training in moderation is always a more healthy approach I feel.
Hope this helps.