Chain problems

Well, about 30 min into the crit (the bell lap for the second prim) I jumped late and missed the simply mac lead out train, but as I did a hard down shift to pull them back I felt a funny pop/skip in my chain. Then the last 10 min of the crit my chain was jumping all over the place. Then in the final sprint I almost went down when my chain jumped gears on me. I didn't think much of it other than my rear derailleur is a bit off. So when I but the bike in the car I was a bit surprised to see my chain. I can't believe it didn't pop and that I didn't crash.

Crit review-

The first crit of the year and I need to do more intervals. The B group started with 16 and by the end of the first lap it was down to 12. By the end of the third lap it was down to 9 or so. Of those remaining 4 road for Simply Mac. So two would attack and the others would do there job. Then we would pull it back together for about two more laps and then nothing. We never put in a good counter attack, because nobody would would work together or attack the simply mac crew. So after we let them recover for a lap (because they set the pace) another two simply mac guys would attack and the game would go again. Then on the last prim three of the mac guys took off and I jump the wheel, but I was a little late and I knew I couldn't get the prim so a couple of us sat up before the line. Big mistake, the front two got a gap of about 30 yards and never looked back. Unfortunately the prim lap was also the three laps to go call. The rest of the group never worked together and we never caught them. They got us by a length. However, after seeing my chain I'm just glad I didn't wreck.