Yasuo's Best Point in a Match?

To begin, I play A LOT of Yasuo. All the matches aside, I seem to notice, at least for me, a huge reduce in power in the mid game. Yasuo's early game is fine, as long as you don't get behind you do well. If you can get a kill, you usually have a huge upper hand in the lane and can freely roam until you are about 3/0. On the flip-side, if you get behind in the lane at all and mid game comes around it's usually the point of no return. My problem is, that around the 15-20 minute mark... suddenly I feel powerless. It doesn't matter the matchup, or how my team or their team is doing at all. I get to a point where I feel like I am not able to put out as much as I am in the early game. But after completing a couple more items, and making it to the 25-30 minute mark... suddenly I'm a force to be reckoned with again. This is the trend throughout 85% of my matches as him. A lot of them have gone from winning to losing hard, and then suddenly rising from the ashes to score a victory. But... this completely contradicts what most people feel about Yasuo. Everyone else it seems says that Yasuo's BEST point is his mid game. Build wise I don't go too crazy, though I've made plenty of my own variants that still give the same effect. I just want to see thoughts honestly, cause I'm starting to wonder if I'm just doing something absurdly wrong.