Your real problem is that you're playing against people that really have pretty much mastered the game and the spawns. MW3 isn't the most noob-friendly of the COD's, so getting into it and staying will probably be tough. By the end of it, it wasn't uncommon for players on here to go 100+/20- kd. Just find some classes you enjoy and use well and figure out the spawns and the lay of the maps.