Hi, what are you talking about ?
You have no way to know for sure what your mmr is, it's totally hidden, websites like op.gg and so on only gives you an estimation.
It's not a bug everyone gets into loss streaks sometimes, and when it happens yes your mmr will tank. Of course if you loose 20 games in a row you're gonna be playing with people in bronze. The best thing to do if you lost let's say 3 games in a row is to stop playing, take a break, play a few normal games and come back to ranked when you're not tilted anymore.
Here are two links for you to read on the subject :
- SoloQ luck ?
- How to win from champ select ? This one is really useful especially the part about dodges, to make it short you SHOULD almost everyday use your first dodge and loose 3LP, in the end you'll gain a lot doing so.