Riot W:L algorithm

So recently I got to 200 wins over 150 losses (I think the actual number was 53 wins over my losses) in ARAM. However, the last week I've had insane losing streaks where the other team has insane comps or I get an afk or I get Xerath and they have all assassins and engage tanks. Now I've lost 28 of my last 40 matches. I admit I'm not the greatest player but I've been getting S A B rank for the most part unless it's just 1 sided or Idk the champ. I've taken several breaks to cool down but a few days later when I come back it's the same thing leading to this unreal w:l record. During the losses where I'm getting good scores the match seems super even or we're at the nexus but then I see a teammate go in 1v5 maybe to buy or they see something I don't and then it's just kinda over. Any idea what's going on with this? Is my (this sounds dumb but) ARAM mmr going through puberty and just changing? I'm on the verge of quitting because this is kinda morale busting [sg-janna]