My Honda is messed up,,,,help please

Hello,
Ok, I went to start my Accord this afternoon and it wouldn't start. It cranked but wouldnt turn over. Also, my "D-4" light in insturment panel was flashing. So, I put it into N and it started, but when I went to put it into d4 to drive it was extremely sluggish. The RPM went up like usual but the power was bad. I got going in first and up but 4 and 3 are pretty bad. Any ideas what is wrong? I did nothing and didnt notice anything wrong the night before when I drove about 30 miles, all was right, till this afternoon. If anyone can help me it would be greatly appreciated. thanks guys!

argh!!