Why am I gaining less LP the more I win?

I was really excited for the start of season 10, mostly because my MMR was thrown off whack to where i was only winning 14-18 points a game... I figured it was mostly due to a losing streak I recently had. Well, starting this season in my provisionals winning my first game. Good start with my first game, until I realized I was placed in Iron 2, Okay no biggie. I play and win my next 3 consecutive games only to find myself winning 41, 39, and 37 LP each game. which roughly put me in Iron 1 ~30LP. I lost my 5th game then won my next 3 to barely put me in Bronze 4 with about 25 LP. My last two games were losses. Since then I have played 4 games, winning 2 (gaining 20 LP each) and losing one (losing 18 LP). Now what is the deal with me winning my most recent game and now only winning 16 LP as now I have a record of 10 wins and 4 Losses. at this rate climbing in soloqueue is going to be impossible. I'd like some answers on what the actual deal is since I play multiple roles and champs and most of my games were in the B to -S category so I'm finding it really hard to believe that I can't get my main account up while on my other accounts i'm gaining 70+ points on provisional wins. This ranked system seems to be getting more and more flawed the more I play on my main account.