Matchmaking?

I'm only a silver player, just play league for fun. the last 2 months matchmaking has been very strange for me. Every single game i play now is filled with platinum and gold players. And my win rate went from probably around 50% to less than a third. I can no longer win games and i get horrible scores nearly every game. Being matched against other silvers I did well nearly all the time getting decent stat lines and carrying games everyonce in a while as trist or tf. But now, i go negative every game, lose lane and get killed in teamfights before i know what is happening. Im getting outplayed by braum as zed. It is not fun anymore, why is this happening?