You gain less than you lose. Bad MMR.
The best way to fix this is to trio Q, and I know, badge of shame..
But just try it for a bit trust me. When your MMR is bad, this is what happens.
You rank is.. lets say you are gold 2, with bad MMR. Your teammates will be roughly Gold5-Gold3 and then other team will be mostly gold3 to even out the match, meaning your team is technically worse than the other team, but you are the better player on your team, your MMR just got you put on this team rather than the other. Now, when you trio queue, normally with players of the same rank or slightly higher than you, you get your MMR slowly fixed, because you start to go up against players more your skill level, will those of your skill level on your team, now this makes for a better quality match, despite you being a three man, I know you don't want to trio, but if you want your MMR fixed this is the best solution, you just need to be winning to fix your MMR, and its even easier to fix it in a trio, not because you win more, but because you atleast are winning against players at and a little above your level. If you were diamond 1 before and are now sitting diamond 5, you shouldn't feel bad about trio-ing anyways..
Good luck with your games buddy, I totally feel you with that badge of shame, it's such a dumb idea..