think it may have somthing to do with a high k/d.
mine is 1.62 and my win/lose ratio dropped from 1.20 to 0.77
I play alot of search and destroy and almost always have 2 people on my team who end the game with zero kills and 4 to 7 deaths. and probably win only 25% of games now even when im the top scorer from both teams.
I don't mind now I just got used to it, im happy to be in the top 3 players.
Same in capture the flag last game I played I whent 38/3 with 8 defends and 2 captures and still lost the game LOL.
I just accept it's going to happen anyway just enjoy the game.
I suggest you find a clan to team up with.
A Tip is to join a friends game when the are in a pre game lobby so u get better people to play with and ur either VS or playing with ur friends always works for me I joined a mates pre-game and that game I went 28-7 with sniper and he went 9-11 so it's hard for them but easy for you and try and make them a friend that's quite a low level. HOPE IT HELPS!!