Winrate just keeps going down…what can I do?

I'm making this post out of my pure inability to comprehend what is going on with my winrate. My WTR is skyrocketing, my WN8 is increasing every session, every stat is increasing by a large margin every day except one: my winrate. Started my account off as a total and complete noob coming from Blitz, but slowly as I played more games I started to get better map knowledge and understand how the game flows in general.

When I started, my winrate was about 30% and my WN8 was about 200. When I started playing more seriously and as I understood the game more, my winrate jumped to about 45-46% and my WN8 about 400-500. Over the past couple days every stat has been increasing steadily but I just cannot win games. Every session ends at about 30% winrate or so, even though most of my matches that day felt…strangely good. I was consistently doing more dmg than my hitpoints, helping heavies, stopping flanks, etc. But every game is just a "I've won the west! Oh, my team lost the 10v4 at the east, time to go back to base and defend I guess." Every match, 5+ games in a row, the team just crumbles. They just crumble into nothing, and I'm left scratching my head.

Now, I'm not writing this post to rant about teammates, but to learn how to improve. Is there anything fundamentally wrong with my approach to increasing my winrate? A video that's gonna help me? Any advice at all? I'm pretty bamboozled right now so anything will help.