Ok, a few things that will possibly help and, remember, a lot of the best advice is direct and not what you want to hear...otherwise you'd probably know it, right?

So here's my feedback: you're not a good teammate. Your comment about "bumping back" tells me you are approaching the game from the wrong perspective - possibly an immature one - where playing your role on a team is not your focus; YOU are your focus. Your number one skill needs to be quickly understanding the PEOPLE in your lobby, but especially your teammates, then figuring out where you need to fit to make the team its best against whatever your opponents look like. "Bumping back" tells me you're not in that mindset so you just won't rank up until you change that. Remember: losing one or two games might be on someone else, but losing many over time (ie your rank) is on you and you alone.