Problems with matchmaking?

I've been playing a lot of ranked solo que, as most people do and probably have been doing more of due to the end of the season coming to a close. Today I played 6 games, and lost them all, despite myself doing well in each and every game, attempting to group, peeling if my role calls for it, and being all together passive and a supportive player with pings and compliments in games. Is there something going on where I am less likely to be on a winning team, am I the problem? I'm very confused because losing 6 games in a row despite a good performance and being demoted near the end of the season is a very frustrating and demoralizing experience. Even yesterday I only won two games out of the five or so I played, even though I again, never went negative or had a negative attitude.

I'm somewhat disheartened by this experience and would just like some kind of tips or something to maybe win a game. Any clues to why this is happening or am I just reading too much end to this in my end of the season struggle to get to gold?