You placement SR isn't based on wins and losses it's based on your last seasons sr and your performance in the matches. It has nothing to do with wins and loses
You gotta focus hard on your accuracy and K/D ratio in your placements to do better. Winning is good, but the game does look at other things when placing you (weapon accuracy is definitely taken into account).
Wanna hear my experience? I was gold and 2600, won 7/10 and got 2900. I got a lot of gold medals in the games I won and lost. And... I was a healer/tank most of the time.
Silver instead of gold because I got DC'd at the beginning of two rounds even though I came back and won all the matches except 1 draw. They counted the DC's as loses.