Plat IV Mid Laner (S5 Diamond V) Looking For Help

So I'm just going to start this post off by saying I am frustrated as heck right now.

I'm a Platinum IV mid lane main that was Diamond V in S5 (climbing up from Silver IV primarily due to spamming Vel'Koz Mid). I had a pretty fantastic winrate on my main champion (77% with over 100 games played), with a good winrate overall. I was pretty excited coming into this new season, ready to climb to Masters and maybe even Challenger.

And then I basically got slapped across the face.

I'm rocking a whooping 31% winrate now. Great, isn't it? I was so salty, and of course my first reaction was to blame my team mates every game. The classic excuses: "they all lost lane hard!", "my team can't rotate worth anything!", "they make the stupidest mistakes!" But as my winrate continued to dwindled, I was forced to realize that it's a problem with me fundamentally that I can't seem to win anymore. I can't pin down the exact problem(s), though, so I've come to ask for help. There are two things, actually, I'd like to ask.

1: Can anyone summarize (or go into detail, I'm not picky) about how this season differs from Season 5 as far as overall goal and "win conditions" go? This is something I evidently don't understand as I can't seem to win even if I get ahead in lane.

2: Would confident players go into Dynamic Queue with me to help me pinpoint my problems? Having a voice communications program would help too, but it's definitely not a requirement.

Thank you very much for reading this far. I hope to get answers soon :)