Silver mmr feels off

So i been binge playing lol at my grandparents house because the pope came to philly so i got nothing to do. Now lets get into my ranked career(pft) I started lol after a friend recommended it since he knew i was a dota 2 beta tester. So i started playing got to level 30 all i wanted to main was fizz. Now the problem with that is because fizz was perma banned every game and so was my backup annie. So i do my placements and i just lose my shit because i can't play fizz so i end up just trolling because lol was not my main game yet. After that i got silver 3(damm son) but i got demoted to bronze 2 after tilting in a binge playing steak during summer. Now there is the current season. I went 6/4 in promos lost like 2 because of trolls and i ended up in bronze 5(fml). So i was like puck riot not gonna play ranked. Do i started playing normals on regular. Then i just started getting into rank again because my toxic ass friends would not leave me alone about being bronze. Now i am silver 4(started from middle and now i am back all my friends still in plat). Ok so my mmr should be good right? because clmbin from bronze 1(start of this vacation) to silver 4(damm son) my mmr should be either silver 3 or higher. I am rolling in with a 70% win rate sometimes higher. So why am i now gaining 17 lp. I don't get why the system is trying to slow u my climbing. I went on a 4 game hot streak like 3 times how can my mmr be bad. IThis reminds me of my mmr when i was stuck in bronze one and was gaining really low amounts of lp even though my games were filled with silver playrs.