0+17=7 and 7+19=16?

Not only that, but for some reason, my mmr is so fucked and weird, that I get 16 points for winning and lose 20 for losing? While it was completely fine the last season, getting 19 for winning and losing at around 16? And overnight it changes this dramatically? I just played two matches in a row and I can understand that the first match could've been technically in minus (Won at 0lp, received 17lp and only had 7?). But the second one? I won that match right after the first one 7lp +19lp and that equals 16? Are you fucking serious? What is wrong with the LP system?