what did you expect? that you’d just keep on winning and have your games remain relatively easy? Let’s get real here.
Of course you’re going to get pitted into more challenging games coming from a win streak. The purpose isn’t for you to LOSE them, but for you to WIN them, that is, if you can. Whether the the difficulty lies in a more challenging opponent(s) or YOU having to carry your team because your teammates are lacking. The series of difficult matches after a win streak can help determine whether or not your win streak was mostly you carrying or you being carried.
It’s the same exact thing when you’re on a losing streak. The matchmaker is that sophisticated and knows how to determine what rank your skill belongs in.
Funny how no one complains during their win streaks and only the losing ones eh?
Be prepared next time after a win streak, keep your cool, do your best and maintain a good K/D win or loss. This should be the same flow throughout every match win AND lose.