LP gains

So, when i started playing ranked this season i had like 60%+ winrate, and then i lost some games and won a few, i stopped playing for 2 weeks or so, when i started playing again i was getting +16 and -16lp, i won 3 or 4 game in a row and in those games i was gaining +17/+18/+19/+20 lp, and when i lost a game after that i lost 20, why is that?