BATTLEFIELD BADCOMPANY2! any help please?

Sup, i play Battlefield Bad company2, my second favourite game of all time, after GTA San andreas, obviously. My question is why does my skill level go to 171? A little while ago i got a 197 skillscore, i left the next game, when i came back on, it says "your skill level is 197", immediately after that, a big fat red "0" comes up to replace the 197. Why is this? I had a bad game a while ago and got 171, now thats on my leaderboard:/ Is there anything i can do? I use to average 190+skill score agame but i went downhill for a few games, but im starting to hit the 4k+games again, any suggestions? Is it the fact that i leave after the good game which resets it to 0? Thanks