Clarity on demotion

I think that there should be a system that tells you if you don't win this game you are going to get demoted because I'll get promoted to Gold IV, as I have multiple times, and sometimes it allows me to lose 2 games at zero points. After that, I get it I should be demoted. Today I had a back and forth day win/lose/win/lose. I had 17 points, I lose a game down to zero. I'm in the 5th from the bottom spot in my division so I think there's no way if I only lose this one game am I'm getting demoted. My logic is this, I'm up 14 wins, I haven't lost multiple games in a row, I should be ok if I lose one game.

Not the case, I lose one game demoted. Mind you, this is the fourth time this season I've gotten to Gold IV and it has never been this ridiculous. If there was a warning on my profile that told me "you will get demoted if you lose next game" then I would have logged off tonight since it was a back and forth day and tried again tomorrow afresh. I would not have opted to play the game but low and behold I'm demoted.

Now I'm not complaining too badly, I know I'll make plat by the end of season with a positive attitude and positive game style of making less mistakes. I just would love some clarity as to why this happens to me every time. It's especially frustrating because I go to Gold IV promotions literally every week with the worst luck ever. I always get ragers/afks in my promos only after i win 5 in a row. Anyways, anybody else have these issues with demotion?