I feel your pain. I have had a similar issue this season.
So, I basically climbed to gold 4, then had a massive losing streak, dropped back to silver 1. Was able to pick myself back up and got back to gold 5. But after I lost 3/5 games in gold 5, I am now losing crazy lp for a loss and barely gaining for a win. Says my mmr is awful, like 1350.
So I hopped on my smurf(I don't consider a smurf just an alt account I used to use to practice champs I wasn't familiar with). Well, anyway, this account was bronze one. I started playing it 1-2 games a day a few weeks ago and already I'm silver 1, and my mmr is 1550ish. So basically my silver 1 account has a much higher mmr then my gold. The issue I have with this is from the start of climbing I always felt my team on my smurf had much better players then my opponents, but on my gold account it was vice versa. Maybe it's just me but it sure is interesting how it's like that every game