So you bassicly win 20 games then you lose the same amount.
Why? Because you get matched with teammates that are weaker than your opponents ( Thats during lose streak). And when you winning, you get amazing team than carries your butt, because enemy team plays very bad.
This stuff never happened in CS:GO for example, you always have w/l/w/l/w/l, since players are on the same skill level. But you see, the situation at LoL is quit fk'ed up, you get to win 20 games in arrow and then you pay back with loses.
Recently i droped from plat 2 to plat 4, and probably will fall to plat 5. But, the funny thing is that, i will end up in plat 2 again in a day or two. Nice matchmaking rito.